Convert.ToChar 方法

定義

命名空間:: System

組件:: mscorlib.dll, System.Runtime.Extensions.dll

組件:: netstandard.dll, System.Runtime.dll

組件:: System.Runtime.Extensions.dll

組件:: mscorlib.dll

組件:: netstandard.dll

重要

部分資訊涉及發行前產品，在發行之前可能會有大幅修改。 Microsoft 對此處提供的資訊，不做任何明確或隱含的瑕疵擔保。

將指定值轉換為 Unicode 字元。

多載

名稱	Description
ToChar(String, IFormatProvider)	將指定字串的第一個字元轉換為 Unicode 字元，並使用指定的文化專用格式資訊。
ToChar(Object)	將指定物件的值轉換為 Unicode 字元。
ToChar(Object, IFormatProvider)	將指定物件的值轉換為其對應的 Unicode 字元，並使用指定的文化特定格式資訊。
ToChar(UInt64)	將指定的 64 位元無符號整數值轉換為其等效的 Unicode 字元。
ToChar(UInt32)	將指定的 32 位元無符號整數值轉換為其等效的 Unicode 字元。
ToChar(UInt16)	將指定的 16 位元無符號整數值轉換為其等效的 Unicode 字元。
ToChar(String)	將指定字串的第一個字元轉換為 Unicode 字元。
ToChar(Single)	呼叫此方法總是拋 InvalidCastException出。
ToChar(SByte)	將指定的 8 位元有符號整數值轉換為其等效的 Unicode 字元。
ToChar(Int64)	將指定的 64 位元有號整數值轉換為其等效的 Unicode 字元。
ToChar(Int16)	將指定的 16 位元有號整數值轉換為其等效的 Unicode 字元。
ToChar(Double)	呼叫此方法總是拋 InvalidCastException出。
ToChar(Decimal)	呼叫此方法總是拋 InvalidCastException出。
ToChar(DateTime)	呼叫此方法總是拋 InvalidCastException出。
ToChar(Char)	回傳指定的 Unicode 字元值;並未進行實際的轉換。
ToChar(Byte)	將指定 8 位元無符號整數的值轉換為其等效的 Unicode 字元。
ToChar(Boolean)	呼叫此方法總是拋 InvalidCastException出。
ToChar(Int32)	將指定的 32 位元有號整數值轉換為其等效的 Unicode 字元。

ToChar(String, IFormatProvider)

來源:: Convert.cs

來源:: Convert.cs

來源:: Convert.cs

來源:: Convert.cs

來源:: Convert.cs

將指定字串的第一個字元轉換為 Unicode 字元，並使用指定的文化專用格式資訊。

public:
 static char ToChar(System::String ^ value, IFormatProvider ^ provider);

public static char ToChar(string value, IFormatProvider provider);

public static char ToChar(string value, IFormatProvider? provider);

static member ToChar : string * IFormatProvider -> char

Public Shared Function ToChar (value As String, provider As IFormatProvider) As Char

參數

value: String

長度為 1 或 null的字串。

provider: IFormatProvider

物件，提供特定文化特性的格式資訊。這個參數已忽略。

傳回

Char

一個 Unicode 字元，等同於中 value第一個也是唯一一個字元。

例外狀況

ArgumentNullException

value 是 null。

FormatException

長度 value 不是1。

範例

以下範例將一個字串表示 Char 值轉換成該 ToChar 方法，並使用 IFormatProvider 一個物件顯示該值被呼叫的格式提供者類型。範例顯示格式提供者未被引用。

using System;
using System.Globalization;

public class DummyProvider : IFormatProvider
{
    // Normally, GetFormat returns an object of the requested type
    // (usually itself) if it is able; otherwise, it returns Nothing.
    public object GetFormat(Type argType)
    {
        // Here, GetFormat displays the name of argType, after removing
        // the namespace information. GetFormat always returns null.
        string argStr = argType.ToString( );
        if( argStr == "" )
            argStr = "Empty";
        argStr = argStr.Substring( argStr.LastIndexOf( '.' ) + 1 );

        Console.Write( "{0,-20}", argStr );
        return null;
    }
}

class ConvertNonNumericProviderDemo
{
    public static void Main( )
    {
        // Create an instance of IFormatProvider.
        DummyProvider provider = new DummyProvider( );
        string format   = "{0,-17}{1,-17}{2}";

        // Convert these values using DummyProvider.
        string Int32A   = "-252645135";
        string DoubleA  = "61680.3855";
        string DayTimeA = "2001/9/11 13:45";

        string BoolA    = "True";
        string StringA  = "Qwerty";
        string CharA    = "$";

        Console.WriteLine( "This example of selected " +
            "Convert.To<Type>( String, IFormatProvider ) \nmethods " +
            "generates the following output. The example displays " +
            "the \nprovider type if the IFormatProvider is called." );
        Console.WriteLine( "\nNote: For the " +
            "ToBoolean, ToString, and ToChar methods, the \n" +
            "IFormatProvider object is not referenced." );

        // The format provider is called for the following conversions.
        Console.WriteLine( );
        Console.WriteLine( format, "ToInt32", Int32A,
            Convert.ToInt32( Int32A, provider ) );
        Console.WriteLine( format, "ToDouble", DoubleA,
            Convert.ToDouble( DoubleA, provider ) );
        Console.WriteLine( format, "ToDateTime", DayTimeA,
            Convert.ToDateTime( DayTimeA, provider ) );

        // The format provider is not called for these conversions.
        Console.WriteLine( );
        Console.WriteLine( format, "ToBoolean", BoolA,
            Convert.ToBoolean( BoolA, provider ) );
        Console.WriteLine( format, "ToString", StringA,
            Convert.ToString( StringA, provider ) );
        Console.WriteLine( format, "ToChar", CharA,
            Convert.ToChar( CharA, provider ) );
    }
}

/*
This example of selected Convert.To<Type>( String, IFormatProvider )
methods generates the following output. The example displays the
provider type if the IFormatProvider is called.

Note: For the ToBoolean, ToString, and ToChar methods, the
IFormatProvider object is not referenced.

NumberFormatInfo    ToInt32          -252645135       -252645135
NumberFormatInfo    ToDouble         61680.3855       61680.3855
DateTimeFormatInfo  ToDateTime       2001/9/11 13:45  9/11/2001 1:45:00 PM

ToBoolean        True             True
ToString         Qwerty           Qwerty
ToChar           $                $
*/

open System
open System.Globalization

type DummyProvider() = 
    interface IFormatProvider with
        // Normally, GetFormat returns an object of the requested type
        // (usually itself) if it is able; otherwise, it returns Nothing.
        member _.GetFormat(argType: Type) =
            // Here, GetFormat displays the name of argType, after removing
            // the namespace information. GetFormat always returns null.
            let argStr = string argType
            let argStr = if argStr = "" then "Empty" else argStr
            let argStr = argStr.Substring(argStr.LastIndexOf '.' + 1)

            printf $"{argStr,-20}"
            null

// Create an instance of IFormatProvider.
let provider =
    { new IFormatProvider with
        // Normally, GetFormat returns an object of the requested type
        // (usually itself) if it is able; otherwise, it returns Nothing.
        member _.GetFormat(argType: Type) =
            // Here, GetFormat displays the name of argType, after removing
            // the namespace information. GetFormat always returns null.
            let argStr = string argType
            let argStr = if argStr = "" then "Empty" else argStr
            let argStr = argStr.Substring(argStr.LastIndexOf '.' + 1)

            printf $"{argStr,-20}"
            null }

let format obj1 obj2 obj3 = printfn $"{obj1,-17}{obj2,-17}{obj3}"

// Convert these values using DummyProvider.
let Int32A   = "-252645135"
let DoubleA  = "61680.3855"
let DayTimeA = "2001/9/11 13:45"

let BoolA    = "True"
let StringA  = "Qwerty"
let CharA    = "$"

printfn 
    """This example of selected Convert.To<Type>( String, IFormatProvider ) 
methods generates the following output. The example displays the 
provider type if the IFormatProvider is called.

Note: For the ToBoolean, ToString, and ToChar methods, the 
IFormatProvider object is not referenced.
"""

// The format provider is called for the following conversions.
format "ToInt32" Int32A (Convert.ToInt32(Int32A, provider) )
format "ToDouble" DoubleA (Convert.ToDouble(DoubleA, provider) )
format "ToDateTime" DayTimeA (Convert.ToDateTime(DayTimeA, provider) )

// The format provider is not called for these conversions.
printfn ""
format "ToBoolean" BoolA (Convert.ToBoolean(BoolA, provider) )
format "ToString" StringA (Convert.ToString(StringA, provider) )
format "ToChar" CharA (Convert.ToChar(CharA, provider) )

// This example of selected Convert.To<Type>( String, IFormatProvider )
// methods generates the following output. The example displays the
// provider type if the IFormatProvider is called.
//
// Note: For the ToBoolean, ToString, and ToChar methods, the
// IFormatProvider object is not referenced.
//
// NumberFormatInfo    ToInt32          -252645135       -252645135
// NumberFormatInfo    ToDouble         61680.3855       61680.3855
// DateTimeFormatInfo  ToDateTime       2001/9/11 13:45  9/11/2001 1:45:00 PM
//
// ToBoolean        True             True
// ToString         Qwerty           Qwerty
// ToChar           $                $

Imports System.Globalization

Public Class DummyProvider
    Implements IFormatProvider

    ' Normally, GetFormat returns an object of the requested type
    ' (usually itself) if it is able; otherwise, it returns Nothing. 
    Public Function GetFormat( argType As Type ) As Object _
        Implements IFormatProvider.GetFormat

        ' Here, GetFormat displays the name of argType, after removing 
        ' the namespace information. GetFormat always returns Nothing.
        Dim argStr  As String = argType.ToString( )
        If argStr = "" Then argStr = "Empty"
        argStr = argStr.Substring( argStr.LastIndexOf( "."c ) + 1 )

        Console.Write( "{0,-20}", argStr )
        Return Nothing

    End Function 
End Class

Module ConvertNonNumericProviderDemo

    Sub Main( )

        ' Create an instance of IFormatProvider.
        Dim provider    As New DummyProvider( )
        Dim format      As String   = "{0,-17}{1,-17}{2}"

        ' Convert these values using DummyProvider.
        Dim Int32A      As String   = "-252645135"   
        Dim DoubleA     As String   = "61680.3855"
        Dim DayTimeA    As String   = "2001/9/11 13:45"

        Dim BoolA       As String   = "True"
        Dim StringA     As String   = "Qwerty"
        Dim CharA       As String   = "$"

        Console.WriteLine( "This example of selected " & _
            "Convert.To<Type>( String, IFormatProvider ) " & vbCrLf & _
            "methods generates the following output. The example " & _
            "displays the " & vbCrLf & "provider type if the " & _
            "IFormatProvider is called." )
        Console.WriteLine( vbCrLf & _
            "Note: For the ToBoolean, ToString, and ToChar " & _
            "methods, the " & vbCrLf & "IFormatProvider object " & _
            "is not referenced." )

        ' The format provider is called for the following conversions.
        Console.WriteLine( )
        Console.WriteLine( format, "ToInt32", Int32A, _
            Convert.ToInt32( Int32A, provider ) )
        Console.WriteLine( format, "ToDouble", DoubleA, _
            Convert.ToDouble( DoubleA, provider ) )
        Console.WriteLine( format, "ToDateTime", DayTimeA, _
            Convert.ToDateTime( DayTimeA, provider ) )

        ' The format provider is not called for these conversions.
        Console.WriteLine( )
        Console.WriteLine( format, "ToBoolean", BoolA, _
            Convert.ToBoolean( BoolA, provider ) )
        Console.WriteLine( format, "ToString", StringA, _
            Convert.ToString( StringA, provider ) )
        Console.WriteLine( format, "ToChar", CharA, _
            Convert.ToChar( CharA, provider ) )

    End Sub
End Module

' This example of selected Convert.To<Type>( String, IFormatProvider )
' methods generates the following output. The example displays the
' provider type if the IFormatProvider is called.
'
' Note: For the ToBoolean, ToString, and ToChar methods, the
' IFormatProvider object is not referenced.
' 
' NumberFormatInfo    ToInt32          -252645135       -252645135
' NumberFormatInfo    ToDouble         61680.3855       61680.3855
' DateTimeFormatInfo  ToDateTime       2001/9/11 13:45  9/11/2001 1:45:00 PM
' 
' ToBoolean        True             True
' ToString         Qwerty           Qwerty
' ToChar           $                $

備註

value 必須是包含單一字元的字串。

如果你不想在轉換失敗時處理例外，可以直接呼叫該 Char.TryParse 方法。它會回傳 Boolean 一個值，表示轉換是否成功。

適用於

ToChar(Object)

來源:: Convert.cs

來源:: Convert.cs

來源:: Convert.cs

來源:: Convert.cs

來源:: Convert.cs

將指定物件的值轉換為 Unicode 字元。

public:
 static char ToChar(System::Object ^ value);

public static char ToChar(object value);

public static char ToChar(object? value);

static member ToChar : obj -> char

Public Shared Function ToChar (value As Object) As Char

參數

value: Object

一個實作介面的 IConvertible 物件。

傳回

Char

一個等價於 value 的 Unicode 字元，若是則value 。null

例外狀況

ArgumentNullException

value 是一個空字串。

InvalidCastException

value 未實作該 IConvertible 介面。

-或-

不支援將轉換為 value a Char 。

OverflowException

value 小於 Char.MinValue 或大於 Char.MaxValue。

範例

以下範例嘗試將物件陣列中的每個元素轉換成一個 Char 值。

object[] values = { 'r', "s", "word", (byte) 83, 77, 109324, 335812911,
                    new DateTime(2009, 3, 10), (uint) 1934,
                    (sbyte) -17, 169.34, 175.6m, null };
char result;

foreach (object value in values)
{
   try {
      result = Convert.ToChar(value);
      Console.WriteLine("The {0} value {1} converts to {2}.",
                        value.GetType().Name, value, result);
   }
   catch (FormatException e) {
      Console.WriteLine(e.Message);
   }
   catch (InvalidCastException) {
      Console.WriteLine("Conversion of the {0} value {1} to a Char is not supported.",
                        value.GetType().Name, value);
   }
   catch (OverflowException) {
      Console.WriteLine("The {0} value {1} is outside the range of the Char data type.",
                        value.GetType().Name, value);
   }
   catch (NullReferenceException) {
      Console.WriteLine("Cannot convert a null reference to a Char.");
   }
}
// The example displays the following output:
//       The Char value r converts to r.
//       The String value s converts to s.
//       String must be exactly one character long.
//       The Byte value 83 converts to S.
//       The Int32 value 77 converts to M.
//       The Int32 value 109324 is outside the range of the Char data type.
//       The Int32 value 335812911 is outside the range of the Char data type.
//       Conversion of the DateTime value 3/10/2009 12:00:00 AM to a Char is not supported.
//       The UInt32 value 1934 converts to ?.
//       The SByte value -17 is outside the range of the Char data type.
//       Conversion of the Double value 169.34 to a Char is not supported.
//       Conversion of the Decimal value 175.6 to a Char is not supported.
//       Cannot convert a null reference to a Char.

let values: obj[] = 
    [| 'r'; "s"; "word"; 83uy; 77; 109324; 335812911
       DateTime(2009, 3, 10); 1934u
       -17y; 169.34; 175.6m; null |]

for value in values do
    try
        let result = Convert.ToChar(value)
        printfn $"The {value.GetType().Name} value {value} converts to {result}."
    with
    | :? FormatException as e ->
        printfn $"{e.Message}"
    | :? InvalidCastException ->
        printfn $"Conversion of the {value.GetType().Name} value {value} to a Char is not supported."
    | :? OverflowException ->
        printfn $"The {value.GetType().Name} value {value} is outside the range of the Char data type."
    | :? NullReferenceException ->
        printfn "Cannot convert a null reference to a Char."
// The example displays the following output:
//       The Char value r converts to r.
//       The String value s converts to s.
//       String must be exactly one character long.
//       The Byte value 83 converts to S.
//       The Int32 value 77 converts to M.
//       The Int32 value 109324 is outside the range of the Char data type.
//       The Int32 value 335812911 is outside the range of the Char data type.
//       Conversion of the DateTime value 3/10/2009 12:00:00 AM to a Char is not supported.
//       The UInt32 value 1934 converts to ?.
//       The SByte value -17 is outside the range of the Char data type.
//       Conversion of the Double value 169.34 to a Char is not supported.
//       Conversion of the Decimal value 175.6 to a Char is not supported.
//       Cannot convert a null reference to a Char.

Dim values() As Object = { "r"c, "s", "word", CByte(83), 77, 109324, _
                           335812911, #3/10/2009#, CUInt(1934), _
                           CSByte(-17), 169.34, 175.6d, Nothing }
Dim result As Char

For Each value As Object In values
   Try
      result = Convert.ToChar(value)
      Console.WriteLine("The {0} value {1} converts to {2}.", _
                        value.GetType().Name, value, result)
   Catch e As FormatException
      Console.WriteLine(e.Message)
   Catch e As InvalidCastException
      Console.WriteLine("Conversion of the {0} value {1} to a Char is not supported.", _
                        value.GetType().Name, value)
   Catch e As OverflowException
      Console.WriteLine("The {0} value {1} is outside the range of the Char data type.", _
                        value.GetType().Name, value)
   Catch e As NullReferenceException
      Console.WriteLine("Cannot convert a null reference to a Char.")
   End Try
Next
' The example displays the following output:
'       The Char value r converts to r.
'       The String value s converts to s.
'       String must be exactly one character long.
'       The Byte value 83 converts to S.
'       The Int32 value 77 converts to M.
'       The Int32 value 109324 is outside the range of the Char data type.
'       The Int32 value 335812911 is outside the range of the Char data type.
'       Conversion of the DateTime value 3/10/2009 12:00:00 AM to a Char is not supported.
'       The UInt32 value 1934 converts to ?.
'       The SByte value -17 is outside the range of the Char data type.
'       Conversion of the Double value 169.34 to a Char is not supported.
'       Conversion of the Decimal value 175.6 to a Char is not supported.
'       Cannot convert a null reference to a Char.

備註

若 value 不是 null，此方法將呼叫包繞至 IConvertible.ToChar 底層類型 value的實作。

適用於

ToChar(Object, IFormatProvider)

來源:: Convert.cs

來源:: Convert.cs

來源:: Convert.cs

來源:: Convert.cs

來源:: Convert.cs

將指定物件的值轉換為其對應的 Unicode 字元，並使用指定的文化特定格式資訊。

public:
 static char ToChar(System::Object ^ value, IFormatProvider ^ provider);

public static char ToChar(object value, IFormatProvider provider);

public static char ToChar(object? value, IFormatProvider? provider);

static member ToChar : obj * IFormatProvider -> char

Public Shared Function ToChar (value As Object, provider As IFormatProvider) As Char

參數

value: Object

一個實作介面的 IConvertible 物件。

provider: IFormatProvider

物件，提供特定文化特性的格式資訊。

傳回

Char

一個等價value於的 Unicode 字元，或若為，則value。null

例外狀況

ArgumentNullException

value 是一個空字串。

InvalidCastException

value 未實作該 IConvertible 介面。

-或-

不支援將轉換為 value a Char 。

OverflowException

value 小於 Char.MinValue 或大於 Char.MaxValue。

範例

以下範例定義了一個實 IConvertible 作的類別和一個實作 IFormatProvider的類別。實作類別的物件會 IConvertible 儲存一組 Double 數值。每個類別中的一個物件會傳遞給方法。ToChar 此方法回Double傳一個字元，其 Unicode 值為數值陣列IFormatProvider的平均值，並利用實作物件來決定如何計算平均值。

using System;
using System.Collections;

// Define the types of averaging available in the class
// implementing IConvertible.
public enum AverageType : short
{
    None = 0,
    GeometricMean = 1,
    ArithmeticMean = 2,
    Median = 3
};

// Pass an instance of this class to methods that require an
// IFormatProvider. The class instance determines the type of
// average to calculate.
public class AverageInfo : IFormatProvider
{
    protected AverageType AvgType;

    // Specify the type of averaging in the constructor.
    public AverageInfo( AverageType avgType )
    {
        this.AvgType = avgType;
    }

    // This method returns a reference to the containing object
    // if an object of AverageInfo type is requested.
    public object GetFormat( Type argType )
    {
        if ( argType == typeof( AverageInfo ) )
            return this;
        else
            return null;
    }

    // Use this property to set or get the type of averaging.
    public AverageType TypeOfAverage
    {
        get { return this.AvgType; }
        set { this.AvgType = value; }
    }
}

// This class encapsulates an array of double values and implements
// the IConvertible interface. Most of the IConvertible methods
// return an average of the array elements in one of three types:
// arithmetic mean, geometric mean, or median.
public class DataSet : IConvertible
{
    protected ArrayList     data;
    protected AverageInfo   defaultProvider;

    // Construct the object and add an initial list of values.
    // Create a default format provider.
    public DataSet( params double[ ] values )
    {
        data = new ArrayList( values );
        defaultProvider =
            new AverageInfo( AverageType.ArithmeticMean );
    }

    // Add additional values with this method.
    public int Add( double value )
    {
        data.Add( value );
        return data.Count;
    }

    // Get, set, and add values with this indexer property.
    public double this[ int index ]
    {
        get
        {
            if( index >= 0 && index < data.Count )
                return (double)data[ index ];
            else
                throw new InvalidOperationException(
                    "[DataSet.get] Index out of range." );
        }
        set
        {
            if( index >= 0 && index < data.Count )
                data[ index ] = value;

            else if( index == data.Count )
                data.Add( value );
            else
                throw new InvalidOperationException(
                    "[DataSet.set] Index out of range." );
        }
    }

    // This property returns the number of elements in the object.
    public int Count
    {
        get { return data.Count; }
    }

    // This method calculates the average of the object's elements.
    protected double Average( AverageType avgType )
    {
        double  SumProd;

        if( data.Count == 0 )
            return 0.0;

        switch( avgType )
        {
            case AverageType.GeometricMean:

                SumProd = 1.0;
                for( int Index = 0; Index < data.Count; Index++ )
                    SumProd *= (double)data[ Index ];

                // This calculation will not fail with negative
                // elements.
                return Math.Sign( SumProd ) * Math.Pow(
                    Math.Abs( SumProd ), 1.0 / data.Count );

            case AverageType.ArithmeticMean:

                SumProd = 0.0;
                for( int Index = 0; Index < data.Count; Index++ )
                    SumProd += (double)data[ Index ];

                return SumProd / data.Count;

            case AverageType.Median:

                if( data.Count % 2 == 0 )
                    return ( (double)data[ data.Count / 2 ] +
                        (double)data[ data.Count / 2 - 1 ] ) / 2.0;
                else
                    return (double)data[ data.Count / 2 ];

            default:
                return 0.0;
        }
    }

    // Get the AverageInfo object from the caller's format provider,
    // or use the local default.
    protected AverageInfo GetAverageInfo( IFormatProvider provider )
    {
        AverageInfo avgInfo = null;

        if( provider != null )
            avgInfo = (AverageInfo)provider.GetFormat(
                typeof( AverageInfo ) );

        if ( avgInfo == null )
            return defaultProvider;
        else
            return avgInfo;
    }

    // Calculate the average and limit the range.
    protected double CalcNLimitAverage( double min, double max,
        IFormatProvider provider )
    {
        // Get the format provider and calculate the average.
        AverageInfo avgInfo = GetAverageInfo( provider );
        double avg = Average( avgInfo.TypeOfAverage );

        // Limit the range, based on the minimum and maximum values
        // for the type.
        return avg > max ? max : avg < min ? min : avg;
    }

    // The following elements are required by IConvertible.

    // None of these conversion functions throw exceptions. When
    // the data is out of range for the type, the appropriate
    // MinValue or MaxValue is used.
    public TypeCode GetTypeCode( )
    {
        return TypeCode.Object;
    }

    public bool ToBoolean( IFormatProvider provider )
    {
        // ToBoolean is false if the dataset is empty.
        if( data.Count <= 0 )
        {
            return false;
        }

        // For median averaging, ToBoolean is true if any
        // non-discarded elements are nonzero.
        else if( AverageType.Median ==
            GetAverageInfo( provider ).TypeOfAverage )
        {
            if (data.Count % 2 == 0 )
                return ( (double)data[ data.Count / 2 ] != 0.0 ||
                    (double)data[ data.Count / 2 - 1 ] != 0.0 );
            else
                return (double)data[ data.Count / 2 ] != 0.0;
        }

        // For arithmetic or geometric mean averaging, ToBoolean is
        // true if any element of the dataset is nonzero.
        else
        {
            for( int Index = 0; Index < data.Count; Index++ )
                if( (double)data[ Index ] != 0.0 )
                    return true;
            return false;
        }
    }

    public byte ToByte( IFormatProvider provider )
    {
        return Convert.ToByte( CalcNLimitAverage(
            Byte.MinValue, Byte.MaxValue, provider ) );
    }

    public char ToChar( IFormatProvider provider )
    {
        return Convert.ToChar( Convert.ToUInt16( CalcNLimitAverage(
            Char.MinValue, Char.MaxValue, provider ) ) );
    }

    // Convert to DateTime by adding the calculated average as
    // seconds to the current date and time. A valid DateTime is
    // always returned.
    public DateTime ToDateTime( IFormatProvider provider )
    {
        double seconds =
            Average( GetAverageInfo( provider ).TypeOfAverage );
        try
        {
            return DateTime.Now.AddSeconds( seconds );
        }
        catch( ArgumentOutOfRangeException )
        {
            return seconds < 0.0 ? DateTime.MinValue : DateTime.MaxValue;
        }
    }

    public decimal ToDecimal( IFormatProvider provider )
    {
        // The Double conversion rounds Decimal.MinValue and
        // Decimal.MaxValue to invalid Decimal values, so the
        // following limits must be used.
        return Convert.ToDecimal( CalcNLimitAverage(
            -79228162514264330000000000000.0,
            79228162514264330000000000000.0, provider ) );
    }

    public double ToDouble( IFormatProvider provider )
    {
        return Average( GetAverageInfo(provider).TypeOfAverage );
    }

    public short ToInt16( IFormatProvider provider )
    {
        return Convert.ToInt16( CalcNLimitAverage(
            Int16.MinValue, Int16.MaxValue, provider ) );
    }

    public int ToInt32( IFormatProvider provider )
    {
        return Convert.ToInt32( CalcNLimitAverage(
            Int32.MinValue, Int32.MaxValue, provider ) );
    }

    public long ToInt64( IFormatProvider provider )
    {
        // The Double conversion rounds Int64.MinValue and
        // Int64.MaxValue to invalid Int64 values, so the following
        // limits must be used.
        return Convert.ToInt64( CalcNLimitAverage(
            -9223372036854775000, 9223372036854775000, provider ) );
    }

    public SByte ToSByte( IFormatProvider provider )
    {
        return Convert.ToSByte( CalcNLimitAverage(
            SByte.MinValue, SByte.MaxValue, provider ) );
    }

    public float ToSingle( IFormatProvider provider )
    {
        return Convert.ToSingle( CalcNLimitAverage(
            Single.MinValue, Single.MaxValue, provider ) );
    }

    public UInt16 ToUInt16( IFormatProvider provider )
    {
        return Convert.ToUInt16( CalcNLimitAverage(
            UInt16.MinValue, UInt16.MaxValue, provider ) );
    }

    public UInt32 ToUInt32( IFormatProvider provider )
    {
        return Convert.ToUInt32( CalcNLimitAverage(
            UInt32.MinValue, UInt32.MaxValue, provider ) );
    }

    public UInt64 ToUInt64( IFormatProvider provider )
    {
        // The Double conversion rounds UInt64.MaxValue to an invalid
        // UInt64 value, so the following limit must be used.
        return Convert.ToUInt64( CalcNLimitAverage(
            0, 18446744073709550000.0, provider ) );
    }

    public object ToType( Type conversionType,
        IFormatProvider provider )
    {
        return Convert.ChangeType( Average(
            GetAverageInfo( provider ).TypeOfAverage ),
            conversionType );
    }

    public string ToString( IFormatProvider provider )
    {
        AverageType avgType = GetAverageInfo( provider ).TypeOfAverage;
        return String.Format( "( {0}: {1:G10} )", avgType,
            Average( avgType ) );
    }
}

class IConvertibleProviderDemo
{
    // Display a DataSet with three different format providers.
    public static void DisplayDataSet( DataSet ds )
    {
        string      fmt    = "{0,-12}{1,20}{2,20}{3,20}";
        AverageInfo median = new AverageInfo( AverageType.Median );
        AverageInfo geMean =
            new AverageInfo( AverageType.GeometricMean );

         // Display the dataset elements.
        if( ds.Count > 0 )
        {
            Console.Write( "\nDataSet: [{0}", ds[ 0 ] );
            for( int iX = 1; iX < ds.Count; iX++ )
                Console.Write( ", {0}", ds[ iX ] );
            Console.WriteLine( "]\n" );
        }

        Console.WriteLine( fmt, "Convert.", "Default",
            "Geometric Mean", "Median");
        Console.WriteLine( fmt, "--------", "-------",
            "--------------", "------");
        Console.WriteLine( fmt, "ToBoolean",
            Convert.ToBoolean( ds, null ),
            Convert.ToBoolean( ds, geMean ),
            Convert.ToBoolean( ds, median ) );
        Console.WriteLine( fmt, "ToByte",
            Convert.ToByte( ds, null ),
            Convert.ToByte( ds, geMean ),
            Convert.ToByte( ds, median ) );
        Console.WriteLine( fmt, "ToChar",
            Convert.ToChar( ds, null ),
            Convert.ToChar( ds, geMean ),
            Convert.ToChar( ds, median ) );
        Console.WriteLine( "{0,-12}{1,20:yyyy-MM-dd HH:mm:ss}" +
            "{2,20:yyyy-MM-dd HH:mm:ss}{3,20:yyyy-MM-dd HH:mm:ss}",
            "ToDateTime", Convert.ToDateTime( ds, null ),
            Convert.ToDateTime( ds, geMean ),
            Convert.ToDateTime( ds, median ) );
        Console.WriteLine( fmt, "ToDecimal",
            Convert.ToDecimal( ds, null ),
            Convert.ToDecimal( ds, geMean ),
            Convert.ToDecimal( ds, median ) );
        Console.WriteLine( fmt, "ToDouble",
            Convert.ToDouble( ds, null ),
            Convert.ToDouble( ds, geMean ),
            Convert.ToDouble( ds, median ) );
        Console.WriteLine( fmt, "ToInt16",
            Convert.ToInt16( ds, null ),
            Convert.ToInt16( ds, geMean ),
            Convert.ToInt16( ds, median ) );
        Console.WriteLine( fmt, "ToInt32",
            Convert.ToInt32( ds, null ),
            Convert.ToInt32( ds, geMean ),
            Convert.ToInt32( ds, median ) );
        Console.WriteLine( fmt, "ToInt64",
            Convert.ToInt64( ds, null ),
            Convert.ToInt64( ds, geMean ),
            Convert.ToInt64( ds, median ) );
        Console.WriteLine( fmt, "ToSByte",
            Convert.ToSByte( ds, null ),
            Convert.ToSByte( ds, geMean ),
            Convert.ToSByte( ds, median ) );
        Console.WriteLine( fmt, "ToSingle",
            Convert.ToSingle( ds, null ),
            Convert.ToSingle( ds, geMean ),
            Convert.ToSingle( ds, median ) );
        Console.WriteLine( fmt, "ToUInt16",
            Convert.ToUInt16( ds, null ),
            Convert.ToUInt16( ds, geMean ),
            Convert.ToUInt16( ds, median ) );
        Console.WriteLine( fmt, "ToUInt32",
            Convert.ToUInt32( ds, null ),
            Convert.ToUInt32( ds, geMean ),
            Convert.ToUInt32( ds, median ) );
        Console.WriteLine( fmt, "ToUInt64",
            Convert.ToUInt64( ds, null ),
            Convert.ToUInt64( ds, geMean ),
            Convert.ToUInt64( ds, median ) );
    }

    public static void Main( )
    {
        Console.WriteLine( "This example of " +
            "the Convert.To<Type>( object, IFormatProvider ) methods " +
            "\ngenerates the following output. The example " +
            "displays the values \nreturned by the methods, " +
            "using several IFormatProvider objects.\n" );

        DataSet ds1 = new DataSet(
            10.5, 22.2, 45.9, 88.7, 156.05, 297.6 );
        DisplayDataSet( ds1 );

        DataSet ds2 = new DataSet(
            359999.95, 425000, 499999.5, 775000, 1695000 );
        DisplayDataSet( ds2 );
    }
}

/*
This example of the Convert.To<Type>( object, IFormatProvider ) methods
generates the following output. The example displays the values
returned by the methods, using several IFormatProvider objects.

DataSet: [10.5, 22.2, 45.9, 88.7, 156.05, 297.6]

Convert.                 Default      Geometric Mean              Median
--------                 -------      --------------              ------
ToBoolean                   True                True                True
ToByte                       103                  59                  67
ToChar                         g                   ;                   C
ToDateTime   2003-05-13 15:04:12 2003-05-13 15:03:28 2003-05-13 15:03:35
ToDecimal       103.491666666667    59.4332135445164                67.3
ToDouble        103.491666666667    59.4332135445164                67.3
ToInt16                      103                  59                  67
ToInt32                      103                  59                  67
ToInt64                      103                  59                  67
ToSByte                      103                  59                  67
ToSingle                103.4917            59.43321                67.3
ToUInt16                     103                  59                  67
ToUInt32                     103                  59                  67
ToUInt64                     103                  59                  67

DataSet: [359999.95, 425000, 499999.5, 775000, 1695000]

Convert.                 Default      Geometric Mean              Median
--------                 -------      --------------              ------
ToBoolean                   True                True                True
ToByte                       255                 255                 255
ToChar                         ?                   ?                   ?
ToDateTime   2003-05-22 07:39:08 2003-05-20 22:28:45 2003-05-19 09:55:48
ToDecimal              750999.89    631577.237188435            499999.5
ToDouble               750999.89    631577.237188435            499999.5
ToInt16                    32767               32767               32767
ToInt32                   751000              631577              500000
ToInt64                   751000              631577              500000
ToSByte                      127                 127                 127
ToSingle                750999.9            631577.3            499999.5
ToUInt16                   65535               65535               65535
ToUInt32                  751000              631577              500000
ToUInt64                  751000              631577              500000
*/

open System
open System.Collections

// Define the types of averaging available in the class
// implementing IConvertible.
type AverageType =
    | None = 0s
    | GeometricMean = 1s
    | ArithmeticMean = 2s
    | Median = 3s

// Pass an instance of this class to methods that require an
// IFormatProvider. The class instance determines the type of
// average to calculate.
[<AllowNullLiteral>]
type AverageInfo(avgType: AverageType) =
    // Use this property to set or get the type of averaging.
    member val TypeOfAverage = avgType with get, set 
    
    interface IFormatProvider with
        // This method returns a reference to the containing object
        // if an object of AverageInfo type is requested.
        member this.GetFormat(argType: Type) =
            if argType = typeof<AverageInfo> then
                this
            else
                null

// This class encapsulates an array of double values and implements
// the IConvertible interface. Most of the IConvertible methods
// an average of the array elements in one of three types:
// arithmetic mean, geometric mean, or median.
type DataSet([<ParamArray>] values: double[]) =
    let data = ResizeArray values
    let defaultProvider =
        AverageInfo AverageType.ArithmeticMean

    // Add additional values with this method.
    member _.Add(value: double) =
        data.Add value
        data.Count

    // Get, set, and add values with this indexer property.
    member _.Item
        with get (index) =
            if index >= 0 && index < data.Count then
                data[index]
            else
                raise (InvalidOperationException "[DataSet.get] Index out of range.")
        and set index value =
            if index >= 0 && index < data.Count then
                data[index] <- value
            elif index = data.Count then
                data.Add value
            else
                raise (InvalidOperationException "[DataSet.set] Index out of range.")

    // This property returns the number of elements in the object.
    member _.Count =
        data.Count

    // This method calculates the average of the object's elements.
    member _.Average(avgType: AverageType) =
        if data.Count = 0 then
            0.0
        else
            match avgType with
            | AverageType.GeometricMean ->
                let sumProd =
                    Seq.reduce ( * ) data
                
                // This calculation will not fail with negative
                // elements.
                (sign sumProd |> float) * Math.Pow(abs sumProd, 1.0 / (float data.Count))

            | AverageType.ArithmeticMean ->
                Seq.average data

            | AverageType.Median ->
                if data.Count % 2 = 0 then
                    (data[data.Count / 2] + data[data.Count / 2 - 1]) / 2.0
                else
                    data[ data.Count / 2]
            | _ ->
                0.0

    // Get the AverageInfo object from the caller's format provider,
    // or use the local default.
    member _.GetAverageInfo(provider: IFormatProvider) =
        let avgInfo =
            if provider <> null then
                provider.GetFormat typeof<AverageInfo> :?> AverageInfo
            else 
                null

        if avgInfo = null then
            defaultProvider
        else
            avgInfo

    // Calculate the average and limit the range.
    member this.CalcNLimitAverage(min: double, max: double, provider: IFormatProvider) =
        // Get the format provider and calculate the average.
        let avgInfo = this.GetAverageInfo provider
        let avg = this.Average avgInfo.TypeOfAverage

        // Limit the range, based on the minimum and maximum values
        // for the type.
        if avg > max then max elif avg < min then min else avg

    // The following elements are required by IConvertible.
    interface IConvertible with
        // None of these conversion functions throw exceptions. When
        // the data is out of range for the type, the appropriate
        // MinValue or MaxValue is used.
        member _.GetTypeCode() =
            TypeCode.Object

        member this.ToBoolean(provider: IFormatProvider) =
            // ToBoolean is false if the dataset is empty.
            if data.Count <= 0 then
                false

            // For median averaging, ToBoolean is true if any
            // non-discarded elements are nonzero.
            elif AverageType.Median = this.GetAverageInfo(provider).TypeOfAverage then
                if data.Count % 2 = 0 then
                    (data[data.Count / 2] <> 0.0 || data[data.Count / 2 - 1] <> 0.0)
                else
                    data[data.Count / 2] <> 0.0

            // For arithmetic or geometric mean averaging, ToBoolean is
            // true if any element of the dataset is nonzero.
            else
                Seq.exists (fun x -> x <> 0.0) data

        member this.ToByte(provider: IFormatProvider) =
            Convert.ToByte(this.CalcNLimitAverage(float Byte.MinValue, float Byte.MaxValue, provider) )

        member this.ToChar(provider: IFormatProvider) =
            Convert.ToChar(Convert.ToUInt16(this.CalcNLimitAverage(float Char.MinValue, float Char.MaxValue, provider) ) )

        // Convert to DateTime by adding the calculated average as
        // seconds to the current date and time. A valid DateTime is
        // always returned.
        member this.ToDateTime(provider: IFormatProvider) =
            let seconds = this.Average(this.GetAverageInfo(provider).TypeOfAverage)
            try
                DateTime.Now.AddSeconds seconds
            with :? ArgumentOutOfRangeException ->
                if seconds < 0.0 then DateTime.MinValue else DateTime.MaxValue

        member this.ToDecimal(provider: IFormatProvider) =
            // The Double conversion rounds Decimal.MinValue and
            // Decimal.MaxValue to invalid Decimal values, so the
            // following limits must be used.
            Convert.ToDecimal(this.CalcNLimitAverage(-79228162514264330000000000000.0, 79228162514264330000000000000.0, provider) )

        member this.ToDouble(provider: IFormatProvider) =
            this.Average(this.GetAverageInfo(provider).TypeOfAverage)

        member this.ToInt16(provider: IFormatProvider) =
            Convert.ToInt16(this.CalcNLimitAverage(float Int16.MinValue, float Int16.MaxValue, provider) )

        member this.ToInt32(provider: IFormatProvider) =
            Convert.ToInt32(this.CalcNLimitAverage(Int32.MinValue, Int32.MaxValue, provider) )

        member this.ToInt64(provider: IFormatProvider) =
            // The Double conversion rounds Int64.MinValue and
            // Int64.MaxValue to invalid Int64 values, so the following
            // limits must be used.
            Convert.ToInt64(this.CalcNLimitAverage(-9223372036854775000., 9223372036854775000., provider) )

        member this.ToSByte(provider: IFormatProvider) =
            Convert.ToSByte(this.CalcNLimitAverage(float SByte.MinValue, float SByte.MaxValue, provider) )

        member this.ToSingle(provider: IFormatProvider) =
            Convert.ToSingle(this.CalcNLimitAverage(float Single.MinValue, float Single.MaxValue, provider) )

        member this.ToUInt16(provider: IFormatProvider) =
            Convert.ToUInt16(this.CalcNLimitAverage(float UInt16.MinValue, float UInt16.MaxValue, provider) )

        member this.ToUInt32(provider: IFormatProvider) =
            Convert.ToUInt32(this.CalcNLimitAverage(float UInt32.MinValue, float UInt32.MaxValue, provider) )

        member this.ToUInt64(provider: IFormatProvider) =
            // The Double conversion rounds UInt64.MaxValue to an invalid
            // UInt64 value, so the following limit must be used.
            Convert.ToUInt64(this.CalcNLimitAverage(0, 18446744073709550000.0, provider) )

        member this.ToType(conversionType: Type, provider: IFormatProvider) =
            Convert.ChangeType(this.Average(this.GetAverageInfo(provider).TypeOfAverage), conversionType)

        member this.ToString(provider: IFormatProvider) =
            let avgType = this.GetAverageInfo(provider).TypeOfAverage
            $"( {avgType}: {this.Average avgType:G10} )"                

// Display a DataSet with three different format providers.
let displayDataSet (ds: DataSet) =
    let fmt obj1 obj2 obj3 obj4 = printfn $"{obj1,-12}{obj2,20}{obj3,20}{obj4,20}"
    let median = AverageInfo AverageType.Median
    let geMean =
        AverageInfo AverageType.GeometricMean

    // Display the dataset elements.
    if ds.Count > 0 then
        printf $"\nDataSet: [{ds[0]}"
        for i = 1 to ds.Count - 1 do
            printf $", {ds[i]}"
        printfn "]\n"

    fmt "Convert." "Default" "Geometric Mean" "Median"
    fmt "--------" "-------" "--------------" "------"
    fmt "ToBoolean"
        (Convert.ToBoolean(ds, null))
        (Convert.ToBoolean(ds, geMean))
        (Convert.ToBoolean(ds, median))
    fmt "ToByte"
        (Convert.ToByte(ds, null))
        (Convert.ToByte(ds, geMean))
        (Convert.ToByte(ds, median))
    fmt "ToChar"
        (Convert.ToChar(ds, null))
        (Convert.ToChar(ds, geMean))
        (Convert.ToChar(ds, median))
    printfn $"""{"ToDateTime",-12}{Convert.ToDateTime(ds, null).ToString "20:yyyy-MM-dd HH:mm:ss"}{Convert.ToDateTime(ds, geMean).ToString "20:yyyy-MM-dd HH:mm:ss"}{Convert.ToDateTime(ds, median).ToString "20:yyyy-MM-dd HH:mm:ss"}"""

    fmt "ToDecimal"
        (Convert.ToDecimal(ds, null))
        (Convert.ToDecimal(ds, geMean))
        (Convert.ToDecimal(ds, median))
    fmt "ToDouble"
        (Convert.ToDouble(ds, null))
        (Convert.ToDouble(ds, geMean))
        (Convert.ToDouble(ds, median))
    fmt "ToInt16"
        (Convert.ToInt16(ds, null))
        (Convert.ToInt16(ds, geMean))
        (Convert.ToInt16(ds, median))
    fmt "ToInt32"
        (Convert.ToInt32(ds, null))
        (Convert.ToInt32(ds, geMean))
        (Convert.ToInt32(ds, median))
    fmt "ToInt64"
        (Convert.ToInt64(ds, null))
        (Convert.ToInt64(ds, geMean))
        (Convert.ToInt64(ds, median))
    fmt "ToSByte"
        (Convert.ToSByte(ds, null))
        (Convert.ToSByte(ds, geMean))
        (Convert.ToSByte(ds, median))
    fmt "ToSingle"
        (Convert.ToSingle(ds, null))
        (Convert.ToSingle(ds, geMean))
        (Convert.ToSingle(ds, median))
    fmt "ToUInt16"
        (Convert.ToUInt16(ds, null))
        (Convert.ToUInt16(ds, geMean))
        (Convert.ToUInt16(ds, median))
    fmt "ToUInt32"
        (Convert.ToUInt32(ds, null))
        (Convert.ToUInt32(ds, geMean))
        (Convert.ToUInt32(ds, median))
    fmt "ToUInt64"
        (Convert.ToUInt64(ds, null))
        (Convert.ToUInt64(ds, geMean))
        (Convert.ToUInt64(ds, median))

printfn
    """This example of the Convert.To<Type>( object, IFormatprovider) methods 
generates the following output. The example displays the values 
returned by the methods, using several IFormatProvider objects.
"""

let ds1 = DataSet(10.5, 22.2, 45.9, 88.7, 156.05, 297.6)
displayDataSet ds1

let ds2 = DataSet(359999.95, 425000, 499999.5, 775000, 1695000)
displayDataSet ds2

// This example of the Convert.To<Type>( object, IFormatprovider) methods
// generates the following output. The example displays the values
// returned by the methods, using several IFormatProvider objects.
//
// DataSet: [10.5, 22.2, 45.9, 88.7, 156.05, 297.6]
//
// Convert.                 Default      Geometric Mean              Median
// --------                 -------      --------------              ------
// ToBoolean                   True                True                True
// ToByte                       103                  59                  67
// ToChar                         g                   ;                   C
// ToDateTime   2003-05-13 15:04:12 2003-05-13 15:03:28 2003-05-13 15:03:35
// ToDecimal       103.491666666667    59.4332135445164                67.3
// ToDouble        103.491666666667    59.4332135445164                67.3
// ToInt16                      103                  59                  67
// ToInt32                      103                  59                  67
// ToInt64                      103                  59                  67
// ToSByte                      103                  59                  67
// ToSingle                103.4917            59.43321                67.3
// ToUInt16                     103                  59                  67
// ToUInt32                     103                  59                  67
// ToUInt64                     103                  59                  67
//
// DataSet: [359999.95, 425000, 499999.5, 775000, 1695000]
//
// Convert.                 Default      Geometric Mean              Median
// --------                 -------      --------------              ------
// ToBoolean                   True                True                True
// ToByte                       255                 255                 255
// ToChar                         ?                   ?                   ?
// ToDateTime   2003-05-22 07:39:08 2003-05-20 22:28:45 2003-05-19 09:55:48
// ToDecimal              750999.89    631577.237188435            499999.5
// ToDouble               750999.89    631577.237188435            499999.5
// ToInt16                    32767               32767               32767
// ToInt32                   751000              631577              500000
// ToInt64                   751000              631577              500000
// ToSByte                      127                 127                 127
// ToSingle                750999.9            631577.3            499999.5
// ToUInt16                   65535               65535               65535
// ToUInt32                  751000              631577              500000
// ToUInt64                  751000              631577              500000

Imports System.Collections

Module IConvertibleProviderDemo

    ' Define the types of averaging available in the class 
    ' implementing IConvertible.
    Enum AverageType as Short
        None = 0
        GeometricMean = 1
        ArithmeticMean = 2
        Median = 3
    End Enum

    ' Pass an instance of this class to methods that require an 
    ' IFormatProvider. The class instance determines the type of 
    ' average to calculate.
    Public Class AverageInfo
        Implements IFormatProvider

        Protected  AvgType      As AverageType

        ' Specify the type of averaging in the constructor.
        Public Sub New( avgType As AverageType )
            Me.AvgType = avgType
        End Sub

        ' This method returns a reference to the containing object 
        ' if an object of AverageInfo type is requested. 
        Public Function GetFormat( argType As Type ) As Object _
            Implements IFormatProvider.GetFormat

            If argType Is GetType( AverageInfo ) Then
                Return Me
            Else
                Return Nothing
            End If
        End Function 

        ' Use this property to set or get the type of averaging.
        Public Property TypeOfAverage( ) As AverageType
            Get
                Return Me.AvgType
            End Get
            Set( ByVal value as AverageType )
                Me.AvgType = value
            End Set
        End Property
    End Class 

    ' This class encapsulates an array of Double values and implements 
    ' the IConvertible interface. Most of the IConvertible methods 
    ' return an average of the array elements in one of three types: 
    ' arithmetic mean, geometric mean, or median. 
    Public Class DataSet
        Implements IConvertible

        Protected data              As ArrayList
        Protected defaultProvider   As AverageInfo
           
        ' Construct the object and add an initial list of values.
        ' Create a default format provider.
        Public Sub New( ParamArray values( ) As Double )
            data = New ArrayList( values )
            defaultProvider = New AverageInfo( _
                AverageType.ArithmeticMean )  
        End Sub
           
        ' Add additional values with this method.
        Public Function Add( value As Double ) As Integer
            data.Add( value )
            Return data.Count
        End Function
           
        ' Get, set, and add values with this indexer property.
        Default Public Property Item(index As Integer) As Double
            Get
                If index >= 0 AndAlso index < data.Count Then
                    Return System.Convert.ToDouble( data( index ) )
                Else
                    Throw New InvalidOperationException( _
                        "[DataSet.get] Index out of range." )
                End If
            End Get
            Set
                If index >= 0 AndAlso index < data.Count Then
                    data( index ) = value
                 
                ElseIf index = data.Count Then
                    data.Add( value )
                Else
                    Throw New InvalidOperationException( _
                        "[DataSet.set] Index out of range." )
                End If
            End Set
        End Property
          
        ' This property returns the number of elements in the object.
        Public ReadOnly Property Count( ) As Integer
            Get
                Return data.Count
            End Get
        End Property

        ' This method calculates the average of the object's elements.
        Protected Function Average( ByVal avgType As AverageType ) As Double

            Dim SumProd As Double 
            Dim Index   As Integer

            If data.Count = 0 Then Return 0.0

            Select Case avgType
                
                Case AverageType.GeometricMean

                    SumProd = 1.0
                    For Index = 0 To data.Count - 1
                        SumProd *= data( Index )
                    Next Index
                    
                    ' This calculation will not fail with negative 
                    ' elements.
                    Return Math.Sign( SumProd ) * Math.Pow( _
                        Math.Abs( SumProd ), 1.0 / data.Count )

                Case AverageType.ArithmeticMean

                    SumProd = 0.0
                    For Index = 0 To data.Count - 1
                        SumProd += data( Index )
                    Next Index

                    Return SumProd / data.Count 

                Case AverageType.Median

                    If data.Count Mod 2 = 0 Then
                        Return ( data( data.Count \ 2 ) + _
                            data( data.Count \ 2 - 1 ) ) / 2.0
                    Else
                        Return data( data.Count \ 2 ) 
                    End If
            End Select
        End Function

        ' Get the AverageInfo object from the caller's format 
        ' provider, or use the local default.
        Protected Function GetAverageInfo( _
            provider As IFormatProvider ) As AverageInfo

            Dim avgInfo As AverageInfo = Nothing

            If Not provider Is Nothing Then
                avgInfo = provider.GetFormat( GetType( AverageInfo ) )
            End If

            Return IIf( avgInfo Is Nothing, defaultProvider, avgInfo )
            
        End Function           

        ' Calculate the average and limit the range.
        Protected Function CalcNLimitAverage( min As Double, _
            max As Double, provider as IFormatProvider ) As Double

            ' Get the format provider and calculate the average.
            Dim avgInfo As AverageInfo = GetAverageInfo( provider )
            Dim avg As Double = Average( avgInfo.TypeOfAverage )

            ' Limit the range, based on the minimum and maximum values 
            ' for the type.
            Return IIf( avg > max, max, IIf( avg < min, min, avg ) )

        End Function

        ' The following elements are required by IConvertible.

        ' None of these conversion functions throw exceptions. When
        ' the data is out of range for the type, the appropriate
        ' MinValue or MaxValue is used.
        Public Function GetTypeCode( ) As TypeCode _
            Implements IConvertible.GetTypeCode
            Return TypeCode.Object
        End Function

        Function ToBoolean( ByVal provider As IFormatProvider ) As _
            Boolean Implements IConvertible.ToBoolean

            ' ToBoolean is false if the dataset is empty.
            If data.Count <= 0 Then
                Return False

            ' For median averaging, ToBoolean is true if any 
            ' non-discarded elements are nonzero.
            ElseIf AverageType.Median = _
                GetAverageInfo( provider ).TypeOfAverage Then

                If data.Count Mod 2 = 0 Then
                    Return ( data( data.Count \ 2 ) <> 0.0 Or _
                        data( data.Count \ 2 - 1 ) <> 0.0 )
                Else
                    Return data( data.Count \ 2 ) <> 0.0
                End If

            ' For arithmetic or geometric mean averaging, ToBoolean is 
            ' true if any element of the dataset is nonzero.  
            Else
                Dim Index As Integer
                For Index = 0 To data.Count - 1
                    If data( Index ) <> 0.0 Then Return True
                Next Index
                Return False
            End If
        End Function

        Function ToByte( ByVal provider As IFormatProvider ) As Byte _
            Implements IConvertible.ToByte
            Return Convert.ToByte( CalcNLimitAverage( _
                Byte.MinValue, Byte.MaxValue, provider ) )
        End Function

        Function ToChar( ByVal provider As IFormatProvider ) As Char _
            Implements IConvertible.ToChar
            Return Convert.ToChar( Convert.ToUInt16( _
                CalcNLimitAverage( 0.0, &HFFFF, provider ) ) )
        End Function

        ' Convert to DateTime by adding the calculated average as 
        ' seconds to the current date and time. A valid DateTime is 
        ' always returned.
        Function ToDateTime( ByVal provider As IFormatProvider ) As _
            DateTime Implements IConvertible.ToDateTime
            Dim seconds As Double = Average( _
                GetAverageInfo( provider ).TypeOfAverage )
            Try
                Return DateTime.Now.AddSeconds( seconds )
            Catch ex As ArgumentOutOfRangeException 
                Return IIf( seconds < 0.0, DateTime.MinValue, _
                    DateTime.MaxValue )
            End Try
        End Function

        Function ToDecimal( ByVal provider As IFormatProvider ) As _
            Decimal Implements IConvertible.ToDecimal

            ' The Double conversion rounds Decimal.MinValue and
            ' Decimal.MaxValue to invalid Decimal values, so the 
            ' following limits must be used.
            Return Convert.ToDecimal( CalcNLimitAverage( _
                -79228162514264330000000000000.0, _
                79228162514264330000000000000.0, provider ) )
        End Function

        Function ToDouble( ByVal provider As IFormatProvider) As _
            Double Implements IConvertible.ToDouble
            Return Average( GetAverageInfo( provider ).TypeOfAverage )
        End Function

        Function ToInt16( ByVal provider As IFormatProvider ) As _
            Short Implements IConvertible.ToInt16
            Return Convert.ToInt16( CalcNLimitAverage( _
                Int16.MinValue, Int16.MaxValue, provider ) )
        End Function

        Function ToInt32( ByVal provider As IFormatProvider ) As _
            Integer Implements IConvertible.ToInt32
            Return Convert.ToInt32( CalcNLimitAverage( _
                Int32.MinValue, Int32.MaxValue, provider ) )
        End Function

        Function ToInt64( ByVal provider As IFormatProvider ) As Long _
            Implements IConvertible.ToInt64

            ' The Double conversion rounds Int64.MinValue and 
            ' Int64.MaxValue to invalid Long values, so the following 
            ' limits must be used.
            Return Convert.ToInt64( CalcNLimitAverage( _
                -9223372036854775000, 9223372036854775000, provider ) )
        End Function

        Function ToSByte( ByVal provider As IFormatProvider ) As _
            SByte Implements IConvertible.ToSByte

            ' SByte.MinValue and SByte.MaxValue are not defined in
            ' Visual Basic.
            Return Convert.ToSByte( CalcNLimitAverage( _
                -128, 127, provider ) )
        End Function

        Function ToSingle( ByVal provider As IFormatProvider ) As _
            Single Implements IConvertible.ToSingle
            Return Convert.ToSingle( CalcNLimitAverage( _
                Single.MinValue, Single.MaxValue, provider ) )
        End Function

        Function ToUInt16( ByVal provider As IFormatProvider ) As _
            UInt16 Implements IConvertible.ToUInt16

            ' UInt16.MinValue and UInt16.MaxValue are not defined in 
            ' Visual Basic.
            Return Convert.ToUInt16( CalcNLimitAverage( _
                0, &HFFFF, provider ) )
        End Function

        Function ToUInt32( ByVal provider As IFormatProvider ) As _
            UInt32 Implements IConvertible.ToUInt32

            ' UInt32.MinValue and UInt32.MaxValue are not defined in 
            ' Visual Basic.
            Return Convert.ToUInt32( CalcNLimitAverage( _
                0, 4294967295, provider ) )
        End Function

        Function ToUInt64( ByVal provider As IFormatProvider ) As _
            UInt64 Implements IConvertible.ToUInt64

            ' UInt64.MinValue and UInt64.MaxValue are not defined in 
            ' Visual Basic. The Double conversion would have rounded 
            ' UInt64.MaxValue, so the following limit must be used.
            Return Convert.ToUInt64( CalcNLimitAverage( _
                0, 18446744073709550000.0, provider ) )
        End Function

        Function ToType( ByVal conversionType As Type, _
            ByVal provider As IFormatProvider) As Object _
            Implements IConvertible.ToType
            Return Convert.ChangeType( Average( GetAverageInfo( _
                provider ).TypeOfAverage ), conversionType )
        End Function

        Overloads Function ToString( ByVal provider As IFormatProvider _
            ) As String Implements IConvertible.ToString
            Dim avgType as AverageType = _
                GetAverageInfo( provider ).TypeOfAverage
            Return String.Format( "( {0}: {1:G10} )", avgType, _
                Average( avgType ) )
        End Function
    End Class
   
    ' Display a DataSet with three different format providers.
    Sub DisplayDataSet( ds As DataSet )

        Dim fmt    As String      = "{0,-12}{1,20}{2,20}{3,20}"
        Dim median As AverageInfo = New AverageInfo( AverageType.Median )
        Dim geMean As AverageInfo = _
            New AverageInfo( AverageType.GeometricMean )
        Dim iX     As Integer

        ' Display the dataset elements.
        If ds.Count > 0 Then
            Console.Write( vbCrLf & "DataSet: [{0}", ds( 0 ) )
            For iX = 1 To ds.Count - 1
                Console.Write( ", {0}", ds( iX ) )
            Next iX
            Console.WriteLine( "]" & vbCrLf )
        End If

        Console.WriteLine( fmt, "Convert.", "Default", _
            "Geometric Mean", "Median" )
        Console.WriteLine( fmt, "--------", "-------", _
            "--------------", "------" )
        Console.WriteLine( fmt, "ToBoolean", _
            Convert.ToBoolean( ds, Nothing ), _
            Convert.ToBoolean( ds, geMean ), _
            Convert.ToBoolean( ds, median ) )
        Console.WriteLine( fmt, "ToByte", _
            Convert.ToByte( ds, Nothing ), _
            Convert.ToByte( ds, geMean ), _
            Convert.ToByte( ds, median ) )
        Console.WriteLine( fmt, "ToChar", _
            Convert.ToChar( ds, Nothing ), _
            Convert.ToChar( ds, geMean ), _
            Convert.ToChar( ds, median ) )
        Console.WriteLine( "{0,-12}{1,20:yyyy-MM-dd HH:mm:ss}" & _
            "{2,20:yyyy-MM-dd HH:mm:ss}{3,20:yyyy-MM-dd HH:mm:ss}", _
            "ToDateTime", Convert.ToDateTime( ds, Nothing ), _
            Convert.ToDateTime( ds, geMean ), _
            Convert.ToDateTime( ds, median ) )
        Console.WriteLine( fmt, "ToDecimal", _
            Convert.ToDecimal( ds, Nothing ), _
            Convert.ToDecimal( ds, geMean ), _
            Convert.ToDecimal( ds, median ) )
        Console.WriteLine( fmt, "ToDouble", _
            Convert.ToDouble( ds, Nothing ), _
            Convert.ToDouble( ds, geMean ), _
            Convert.ToDouble( ds, median ) )
        Console.WriteLine( fmt, "ToInt16", _
            Convert.ToInt16( ds, Nothing ), _
            Convert.ToInt16( ds, geMean ), _
            Convert.ToInt16( ds, median ) )
        Console.WriteLine( fmt, "ToInt32", _
            Convert.ToInt32( ds, Nothing ), _
            Convert.ToInt32( ds, geMean ), _
            Convert.ToInt32( ds, median ) )
        Console.WriteLine( fmt, "ToInt64", _
            Convert.ToInt64( ds, Nothing ), _
            Convert.ToInt64( ds, geMean ), _
            Convert.ToInt64( ds, median ) )
        Console.WriteLine( fmt, "ToSByte", _
            Convert.ToSByte( ds, Nothing ), _
            Convert.ToSByte( ds, geMean ), _
            Convert.ToSByte( ds, median ) )
        Console.WriteLine( fmt, "ToSingle", _
            Convert.ToSingle( ds, Nothing ), _
            Convert.ToSingle( ds, geMean ), _
            Convert.ToSingle( ds, median ) )
        Console.WriteLine( fmt, "ToUInt16", _
            Convert.ToUInt16( ds, Nothing ), _
            Convert.ToUInt16( ds, geMean ), _
            Convert.ToUInt16( ds, median ) )
        Console.WriteLine( fmt, "ToUInt32", _
            Convert.ToUInt32( ds, Nothing ), _
            Convert.ToUInt32( ds, geMean ), _
            Convert.ToUInt32( ds, median ) )
        Console.WriteLine( fmt, "ToUInt64", _
            Convert.ToUInt64( ds, Nothing ), _
            Convert.ToUInt64( ds, geMean ), _
            Convert.ToUInt64( ds, median ) )
    End Sub
   
    Sub Main( )
        Console.WriteLine( _
            "This example of the Convert.To<Type>( Object, " & _
            "IFormatProvider ) methods " & vbCrLf & "generates " & _
            "the following output. The example displays the " & _
            "values " & vbCrLf & "returned by the methods, " & _
            "using several IFormatProvider objects." & vbCrLf )
          
        Dim ds1 As New DataSet( 10.5, 22.2, 45.9, 88.7, 156.05, 297.6 )
        DisplayDataSet( ds1 )
          
        Dim ds2 As New DataSet( _
            359999.95, 425000, 499999.5, 775000, 1695000 )
        DisplayDataSet( ds2 )
    End Sub 
End Module 

' This example of the Convert.To<Type>( Object, IFormatProvider ) methods
' generates the following output. The example displays the values
' returned by the methods, using several IFormatProvider objects.
' 
' DataSet: [10.5, 22.2, 45.9, 88.7, 156.05, 297.6]
' 
' Convert.                 Default      Geometric Mean              Median
' --------                 -------      --------------              ------
' ToBoolean                   True                True                True
' ToByte                       103                  59                  67
' ToChar                         g                   ;                   C
' ToDateTime   2003-05-13 14:52:53 2003-05-13 14:52:09 2003-05-13 14:52:17
' ToDecimal       103.491666666667    59.4332135445164                67.3
' ToDouble        103.491666666667    59.4332135445164                67.3
' ToInt16                      103                  59                  67
' ToInt32                      103                  59                  67
' ToInt64                      103                  59                  67
' ToSByte                      103                  59                  67
' ToSingle                103.4917            59.43321                67.3
' ToUInt16                     103                  59                  67
' ToUInt32                     103                  59                  67
' ToUInt64                     103                  59                  67
' 
' DataSet: [359999.95, 425000, 499999.5, 775000, 1695000]
' 
' Convert.                 Default      Geometric Mean              Median
' --------                 -------      --------------              ------
' ToBoolean                   True                True                True
' ToByte                       255                 255                 255
' ToChar                         ?                   ?                   ?
' ToDateTime   2003-05-22 07:27:49 2003-05-20 22:17:27 2003-05-19 09:44:29
' ToDecimal              750999.89    631577.237188435            499999.5
' ToDouble               750999.89    631577.237188435            499999.5
' ToInt16                    32767               32767               32767
' ToInt32                   751000              631577              500000
' ToInt64                   751000              631577              500000
' ToSByte                      127                 127                 127
' ToSingle                750999.9            631577.3            499999.5
' ToUInt16                   65535               65535               65535
' ToUInt32                  751000              631577              500000
' ToUInt64                  751000              631577              500000

備註

回傳值是調 IConvertible.ToChar 用底層類型 value方法的結果。

provider 使用者能指定關於內容 value的文化專屬轉換資訊。基礎型別 provider忽略;但若 value 是實作 IConvertible 介面的使用者定義型別，則可使用此參數。

適用於

ToChar(UInt64)

來源:: Convert.cs

來源:: Convert.cs

來源:: Convert.cs

來源:: Convert.cs

來源:: Convert.cs

重要

此 API 不符合 CLS 規範。

將指定的 64 位元無符號整數值轉換為其等效的 Unicode 字元。

public:
 static char ToChar(System::UInt64 value);

[System.CLSCompliant(false)]
public static char ToChar(ulong value);

[<System.CLSCompliant(false)>]
static member ToChar : uint64 -> char

Public Shared Function ToChar (value As ULong) As Char

參數

value: UInt64

64 位元無符號整數用於轉換。

傳回

Char

一個等價 value於的 Unicode 字元。

屬性: CLSCompliantAttribute

例外狀況

OverflowException

value 大於 Char.MaxValue。

範例

以下範例將一個無符號長整數陣列中的每個元素轉換為一個 Char 值。

ulong[] numbers = { UInt64.MinValue, 40, 160, 255, 1028,
                    2011, 30001, 207154, Int64.MaxValue };
char result;
foreach (ulong number in numbers)
{
   try {
      result = Convert.ToChar(number);
      Console.WriteLine("{0} converts to '{1}'.", number, result);
   }
   catch (OverflowException) {
      Console.WriteLine("{0} is outside the range of the Char data type.",
                        number);
   }
}
// The example displays the following output:
//       0 converts to ' '.
//       40 converts to '('.
//       160 converts to ' '.
//       255 converts to 'ÿ'.
//       1028 converts to 'Є'.
//       2011 converts to 'ߛ'.
//       30001 converts to '由'.
//       207154 is outside the range of the Char data type.
//       9223372036854775807 is outside the range of the Char data type.

let numbers =
    [| UInt64.MinValue; 40uL; 160uL; 255uL; 1028uL
       2011uL; 30001uL; 207154uL; uint64 Int64.MaxValue |]
for number in numbers do
    try
        let result = Convert.ToChar number
        printfn $"{number} converts to '{result}'." 
    with :? OverflowException ->
        printfn $"{number} is outside the range of the Char data type."
// The example displays the following output:
//       0 converts to ' '.
//       40 converts to '('.
//       160 converts to ' '.
//       255 converts to 'ÿ'.
//       1028 converts to 'Є'.
//       2011 converts to 'ߛ'.
//       30001 converts to '由'.
//       207154 is outside the range of the Char data type.
//       9223372036854775807 is outside the range of the Char data type.

Dim numbers() As ULong = { UInt64.MinValue, 40, 160, 255, 1028, _
                              2011, 30001, 207154, Int64.MaxValue }
Dim result As Char
For Each number As ULong In numbers
   Try
      result = Convert.ToChar(number)
      Console.WriteLine("{0} converts to '{1}'.", number, result)
   Catch e As OverflowException
      Console.WriteLine("{0} is outside the range of the Char data type.", _
                        number)
   End Try
Next
' The example displays the following output:
'       0 converts to ' '.
'       40 converts to '('.
'       160 converts to ' '.
'       255 converts to 'ÿ'.
'       1028 converts to 'Є'.
'       2011 converts to 'ߛ'.
'       30001 converts to '由'.
'       207154 is outside the range of the Char data type.
'       9223372036854775807 is outside the range of the Char data type.

適用於

ToChar(UInt32)

來源:: Convert.cs

來源:: Convert.cs

來源:: Convert.cs

來源:: Convert.cs

來源:: Convert.cs

重要

此 API 不符合 CLS 規範。

將指定的 32 位元無符號整數值轉換為其等效的 Unicode 字元。

public:
 static char ToChar(System::UInt32 value);

[System.CLSCompliant(false)]
public static char ToChar(uint value);

[<System.CLSCompliant(false)>]
static member ToChar : uint32 -> char

Public Shared Function ToChar (value As UInteger) As Char

參數

value: UInt32

32位元無符號整數要轉換。

傳回

Char

一個等價 value於的 Unicode 字元。

屬性: CLSCompliantAttribute

例外狀況

OverflowException

value 大於 Char.MaxValue。

範例

以下範例將一個無符號整數陣列中的每個元素轉換成一個 Char 值。

uint[] numbers = { UInt32.MinValue, 40, 160, 255, 1028,
                   2011, 30001, 207154, Int32.MaxValue };
char result;
foreach (uint number in numbers)
{
   try {
      result = Convert.ToChar(number);
      Console.WriteLine("{0} converts to '{1}'.", number, result);
   }
   catch (OverflowException) {
      Console.WriteLine("{0} is outside the range of the Char data type.",
                        number);
   }
}
// The example displays the following output:
//       0 converts to ' '.
//       40 converts to '('.
//       160 converts to ' '.
//       255 converts to 'ÿ'.
//       1028 converts to 'Є'.
//       2011 converts to 'ߛ'.
//       30001 converts to '由'.
//       207154 is outside the range of the Char data type.
//       2147483647 is outside the range of the Char data type.

let numbers =
    [| UInt32.MinValue; 40u; 160u; 255u; 1028u
       2011u; 30001u; 207154u; uint Int32.MaxValue |]
for number in numbers do
    try
        let result = Convert.ToChar number
        printfn $"{number} converts to '{result}'." 
    with :? OverflowException ->
        printfn $"{number} is outside the range of the Char data type."
// The example displays the following output:
//       0 converts to ' '.
//       40 converts to '('.
//       160 converts to ' '.
//       255 converts to 'ÿ'.
//       1028 converts to 'Є'.
//       2011 converts to 'ߛ'.
//       30001 converts to '由'.
//       207154 is outside the range of the Char data type.
//       2147483647 is outside the range of the Char data type.

Dim numbers() As UInteger = { UInt32.MinValue, 40, 160, 255, 1028, _
                              2011, 30001, 207154, Int32.MaxValue }
Dim result As Char
For Each number As UInteger In numbers
   Try
      result = Convert.ToChar(number)
      Console.WriteLine("{0} converts to '{1}'.", number, result)
   Catch e As OverflowException
      Console.WriteLine("{0} is outside the range of the Char data type.", _
                        number)
   End Try
Next
' The example displays the following output:
'       0 converts to ' '.
'       40 converts to '('.
'       160 converts to ' '.
'       255 converts to 'ÿ'.
'       1028 converts to 'Є'.
'       2011 converts to 'ߛ'.
'       30001 converts to '由'.
'       207154 is outside the range of the Char data type.
'       2147483647 is outside the range of the Char data type.

適用於

ToChar(UInt16)

來源:: Convert.cs

來源:: Convert.cs

來源:: Convert.cs

來源:: Convert.cs

來源:: Convert.cs

重要

此 API 不符合 CLS 規範。

將指定的 16 位元無符號整數值轉換為其等效的 Unicode 字元。

public:
 static char ToChar(System::UInt16 value);

[System.CLSCompliant(false)]
public static char ToChar(ushort value);

[<System.CLSCompliant(false)>]
static member ToChar : uint16 -> char

Public Shared Function ToChar (value As UShort) As Char

參數

value: UInt16

16位元無符號整數要轉換。

傳回

Char

一個等價 value於的 Unicode 字元。

屬性: CLSCompliantAttribute

範例

以下範例將一個無符號 16 位元整數陣列中的每個元素轉換為一個 Char 值。

ushort[] numbers = { UInt16.MinValue, 40, 160, 255, 1028,
                     2011, UInt16.MaxValue };
char result;
foreach (ushort number in numbers)
{
   result = Convert.ToChar(number);
   Console.WriteLine("{0} converts to '{1}'.", number, result);
}
// The example displays the following output:
//       0 converts to ' '.
//       40 converts to '('.
//       160 converts to ' '.
//       255 converts to 'ÿ'.
//       1028 converts to 'Є'.
//       2011 converts to 'ߛ'.
//       65535 converts to ''.

let numbers = 
    [| UInt16.MinValue; 40us; 160us; 255us
       1028us; 2011us; UInt16.MaxValue |]
for number in numbers do
    let result = Convert.ToChar number
    printfn $"{number} converts to '{result}'." 
// The example displays the following output:
//       0 converts to ' '.
//       40 converts to '('.
//       160 converts to ' '.
//       255 converts to 'ÿ'.
//       1028 converts to 'Є'.
//       2011 converts to 'ߛ'.
//       65535 converts to ''.

Dim numbers() As UShort = { UInt16.MinValue, 40, 160, 255, 1028, _
                            2011, UInt16.MaxValue }
Dim result As Char
For Each number As UShort In numbers
   result = Convert.ToChar(number)
   Console.WriteLine("{0} converts to '{1}'.", number, result)
Next
' The example displays the following output:
'       0 converts to ' '.
'       40 converts to '('.
'       160 converts to ' '.
'       255 converts to 'ÿ'.
'       1028 converts to 'Є'.
'       2011 converts to 'ߛ'.
'       65535 converts to ''.

適用於

ToChar(String)

來源:: Convert.cs

來源:: Convert.cs

來源:: Convert.cs

來源:: Convert.cs

來源:: Convert.cs

將指定字串的第一個字元轉換為 Unicode 字元。

public:
 static char ToChar(System::String ^ value);

public static char ToChar(string value);

static member ToChar : string -> char

Public Shared Function ToChar (value As String) As Char

參數

value: String

長度為 1 的串。

傳回

Char

一個 Unicode 字元，等同於中 value第一個也是唯一一個字元。

例外狀況

ArgumentNullException

value 是 null。

FormatException

長度 value 不是1。

範例

以下範例將字串陣列中的每個元素轉換為一個 Char 值。

string nullString = null;
string[] strings = { "A", "This",  '\u0007'.ToString(), nullString };
char result;
foreach (string strng in strings)
{
   try {
      result = Convert.ToChar(strng);
      Console.WriteLine("'{0}' converts to '{1}'.", strng, result);
   }
   catch (FormatException)
   {
      Console.WriteLine("'{0}' is not in the correct format for conversion to a Char.",
                        strng);
   }
   catch (ArgumentNullException) {
      Console.WriteLine("A null string cannot be converted to a Char.");
   }
}
// The example displays the following output:
//       'A' converts to 'A'.
//       'This' is not in the correct format for conversion to a Char.
//       '       ' converts to ' '.
//       A null string cannot be converted to a Char.

let nullString = null
let strings = [| "A"; "This";  '\u0007'.ToString(); nullString |]
for string in strings do
    try
        let result = Convert.ToChar string
        printfn $"'{string}' converts to '{result}'."
    with 
    | :? FormatException ->
        printfn $"'{string}' is not in the correct format for conversion to a Char."
    | :? ArgumentNullException ->
        printfn "A null string cannot be converted to a Char."
// The example displays the following output:
//       'A' converts to 'A'.
//       'This' is not in the correct format for conversion to a Char.
//       '       ' converts to ' '.
//       A null string cannot be converted to a Char.

Dim nullString As String = Nothing
Dim strings() As String = { "A", "This", vbTab, nullString }
Dim result As Char
For Each strng As String In strings
   Try
      result = Convert.ToChar(strng)
      Console.WriteLine("'{0}' converts to '{1}'.", strng, result)
   Catch e As FormatException
      Console.WriteLine("'{0}' is not in the correct format for conversion to a Char.", _
                        strng)
   Catch e As ArgumentNullException
      Console.WriteLine("A null string cannot be converted to a Char.")
   End Try
Next
' The example displays the following output:
'       'A' converts to 'A'.
'       'This' is not in the correct format for conversion to a Char.
'       '       ' converts to ' '.
'       A null string cannot be converted to a Char.

備註

value 必須是包含單一字元的字串。

如果你不想在轉換失敗時處理例外，可以直接呼叫該 Char.TryParse 方法。它會回傳 Boolean 一個值，表示轉換是否成功。

適用於

ToChar(Single)

來源:: Convert.cs

來源:: Convert.cs

來源:: Convert.cs

來源:: Convert.cs

來源:: Convert.cs

呼叫此方法總是拋 InvalidCastException出。

public:
 static char ToChar(float value);

public static char ToChar(float value);

static member ToChar : single -> char

Public Shared Function ToChar (value As Single) As Char

參數

value: Single

要轉換的單精度浮點數。

傳回

Char

此轉換不被支援。沒有任何價值回傳。

例外狀況

InvalidCastException

此轉換不被支援。

適用於

ToChar(SByte)

來源:: Convert.cs

來源:: Convert.cs

來源:: Convert.cs

來源:: Convert.cs

來源:: Convert.cs

重要

此 API 不符合 CLS 規範。

將指定的 8 位元有符號整數值轉換為其等效的 Unicode 字元。

public:
 static char ToChar(System::SByte value);

[System.CLSCompliant(false)]
public static char ToChar(sbyte value);

[<System.CLSCompliant(false)>]
static member ToChar : sbyte -> char

Public Shared Function ToChar (value As SByte) As Char

參數

value: SByte

8位元有符號整數用於轉換。

傳回

Char

一個等價 value於的 Unicode 字元。

屬性: CLSCompliantAttribute

例外狀況

OverflowException

value 小於 Char.MinValue。

範例

以下範例將一個有符號位元組陣列轉換為 Char 值。

sbyte[] numbers = { SByte.MinValue, -1, 40, 80, 120, SByte.MaxValue };
char result;
foreach (sbyte number in numbers)
{
   try {
      result = Convert.ToChar(number);
      Console.WriteLine("{0} converts to '{1}'.", number, result);
   }
   catch (OverflowException) {
      Console.WriteLine("{0} is outside the range of the Char data type.",
                        number);
   }
}
// The example displays the following output:
//       -128 is outside the range of the Char data type.
//       -1 is outside the range of the Char data type.
//       40 converts to '('.
//       80 converts to 'P'.
//       120 converts to 'x'.
//       127 converts to '⌂'.

let numbers =
    [| SByte.MinValue; -1y; 40y; 80y; 120y; SByte.MaxValue |]
for number in numbers do
    try
        let result = Convert.ToChar number
        printfn $"{number} converts to '{result}'." 
    with :? OverflowException ->
        printfn $"{number} is outside the range of the Char data type."
// The example displays the following output:
//       -128 is outside the range of the Char data type.
//       -1 is outside the range of the Char data type.
//       40 converts to '('.
//       80 converts to 'P'.
//       120 converts to 'x'.
//       127 converts to '⌂'.

Dim numbers() As SByte = { SByte.MinValue, -1, 40, 80, 120, SByte.MaxValue }
Dim result As Char
For Each number As SByte In numbers
   Try
      result = Convert.ToChar(number)
      Console.WriteLine("{0} converts to '{1}'.", number, result)
   Catch e As OverflowException
      Console.WriteLine("{0} is outside the range of the Char data type.", _
                        number)
   End Try
Next
' The example displays the following output:
'       -128 is outside the range of the Char data type.
'       -1 is outside the range of the Char data type.
'       40 converts to '('.
'       80 converts to 'P'.
'       120 converts to 'x'.
'       127 converts to '⌂'.

適用於

ToChar(Int64)

來源:: Convert.cs

來源:: Convert.cs

來源:: Convert.cs

來源:: Convert.cs

來源:: Convert.cs

將指定的 64 位元有號整數值轉換為其等效的 Unicode 字元。

public:
 static char ToChar(long value);

public static char ToChar(long value);

static member ToChar : int64 -> char

Public Shared Function ToChar (value As Long) As Char

參數

value: Int64

要轉換的64位帶正負號整數。

傳回

Char

一個等價 value於的 Unicode 字元。

例外狀況

OverflowException

value 小於 Char.MinValue 或大於 Char.MaxValue。

範例

以下範例嘗試將一個長整數轉換成 Char，並在失敗時拋出 a OverflowException 。

public void ConvertLongChar(long longVal) {

    char	charVal = 'a';

    try {
        charVal = System.Convert.ToChar(longVal);
        System.Console.WriteLine("{0} as a char is {1}",
            longVal, charVal);
    }
    catch (System.OverflowException) {
        System.Console.WriteLine(
            "Overflow in long-to-char conversion.");
    }
    
    // A conversion from Char to long cannot overflow.
    longVal = System.Convert.ToInt64(charVal);
    System.Console.WriteLine("{0} as an Int64 is {1}",
        charVal, longVal);
}

let convertLongChar (longVal: int64) =
    let charVal = 'a'

    try
        let charVal = Convert.ToChar longVal
        printfn $"{longVal} as a char is {charVal}"
    with :? OverflowException ->
        printfn "Overflow in long-to-char conversion."

    // A conversion from Char to long cannot overflow.
    let longVal = Convert.ToInt64 charVal
    printfn $"{charVal} as an Int64 is {longVal}"

Public Sub ConvertLongChar(ByVal longVal As Long)

    Dim charVal As Char = "a"c

    Try
        charVal = System.Convert.ToChar(longVal)
        System.Console.WriteLine("{0} as a char is {1}", _
                                  longVal, charVal)
    Catch exception As System.OverflowException
        System.Console.WriteLine( _
            "Overflow in Long-to-Char conversion.")
    End Try

    ' A conversion from Char to Long cannot overflow.
    longVal = System.Convert.ToInt64(charVal)
    System.Console.WriteLine("{0} as a Long is {1}", _
                              charVal, longVal)
End Sub

適用於

ToChar(Int16)

來源:: Convert.cs

來源:: Convert.cs

來源:: Convert.cs

來源:: Convert.cs

來源:: Convert.cs

將指定的 16 位元有號整數值轉換為其等效的 Unicode 字元。

public:
 static char ToChar(short value);

public static char ToChar(short value);

static member ToChar : int16 -> char

Public Shared Function ToChar (value As Short) As Char

參數

value: Int16

要轉換的16位帶正負號整數。

傳回

Char

一個等價 value於的 Unicode 字元。

例外狀況

OverflowException

value 小於 Char.MinValue。

範例

以下範例將一組有符號的 16 位元整數陣列轉換為 Char 值。

short[] numbers = { Int16.MinValue, 0, 40, 160, 255, 1028,
                    2011, Int16.MaxValue };
char result;
foreach (short number in numbers)
{
   try {
      result = Convert.ToChar(number);
      Console.WriteLine("{0} converts to '{1}'.", number, result);
   }
   catch (OverflowException) {
      Console.WriteLine("{0} is outside the range of the Char data type.",
                        number);
   }
}
// The example displays the following output:
//       -32768 is outside the range of the Char data type.
//       0 converts to ' '.
//       40 converts to '('.
//       160 converts to ' '.
//       255 converts to 'ÿ'.
//       1028 converts to 'Є'.
//       2011 converts to 'ߛ'.
//       32767 converts to '翿'.

let numbers = 
    [| Int16.MinValue; 0s; 40s; 160s 
       255s; 1028s; 2011s; Int16.MaxValue |]
for number in numbers do
    try
        let result = Convert.ToChar number
        printfn $"{number} converts to '{result}'." 
    with :? OverflowException ->
    printfn $"{number} is outside the range of the Char data type."
// The example displays the following output:
//       -32768 is outside the range of the Char data type.
//       0 converts to ' '.
//       40 converts to '('.
//       160 converts to ' '.
//       255 converts to 'ÿ'.
//       1028 converts to 'Є'.
//       2011 converts to 'ߛ'.
//       32767 converts to '翿'.

Dim numbers() As Short = { Int16.MinValue, 0, 40, 160, 255, 1028, _
                           2011, Int16.MaxValue }
Dim result As Char
For Each number As Short In numbers
   Try
      result = Convert.ToChar(number)
      Console.WriteLine("{0} converts to '{1}'.", number, result)
   Catch e As OverflowException
      Console.WriteLine("{0} is outside the range of the Char data type.", _
                        number)
   End Try
Next
' The example displays the following output:
'       -32768 is outside the range of the Char data type.
'       0 converts to ' '.
'       40 converts to '('.
'       160 converts to ' '.
'       255 converts to 'ÿ'.
'       1028 converts to 'Є'.
'       2011 converts to 'ߛ'.
'       32767 converts to '翿'.

適用於

ToChar(Double)

來源:: Convert.cs

來源:: Convert.cs

來源:: Convert.cs

來源:: Convert.cs

來源:: Convert.cs

呼叫此方法總是拋 InvalidCastException出。

public:
 static char ToChar(double value);

public static char ToChar(double value);

static member ToChar : double -> char

Public Shared Function ToChar (value As Double) As Char

參數

value: Double

要轉換的雙精度浮點數。

傳回

Char

此轉換不被支援。沒有任何價值回傳。

例外狀況

InvalidCastException

此轉換不被支援。

適用於

ToChar(Decimal)

來源:: Convert.cs

來源:: Convert.cs

來源:: Convert.cs

來源:: Convert.cs

來源:: Convert.cs

呼叫此方法總是拋 InvalidCastException出。

public:
 static char ToChar(System::Decimal value);

public static char ToChar(decimal value);

static member ToChar : decimal -> char

Public Shared Function ToChar (value As Decimal) As Char

參數

value: Decimal

用小數轉換。

傳回

Char

此轉換不被支援。沒有任何價值回傳。

例外狀況

InvalidCastException

此轉換不被支援。

範例

以下範例嘗試將 a Decimal 轉換為 Char，並投 InvalidCastException 擲失敗。

public void ConvertCharDecimal(char charVal) {
    Decimal decimalVal = 0;
    
    // Char to decimal conversion is not supported and will always
    // throw an InvalidCastException.
    try {
        decimalVal = System.Convert.ToDecimal(charVal);
    }
    catch (System.InvalidCastException) {
        System.Console.WriteLine(
            "Char-to-Decimal conversion is not supported " +
            "by the .NET Framework.");
    }

    //Decimal to char conversion is also not supported.
    try {
        charVal = System.Convert.ToChar(decimalVal);
    }
    catch (System.InvalidCastException) {
        System.Console.WriteLine(
            "Decimal-to-Char conversion is not supported " +
            "by the .NET Framework.");
    }
}

let convertCharDecimal (charVal: char) =
    let decimalVal = 0m

    // Char to decimal conversion is not supported and will always
    // throw an InvalidCastException.
    try
        let decimalVal = Convert.ToDecimal charVal
        ()
    with :? InvalidCastException ->
        printfn "Char-to-Decimal conversion is not supported by the .NET Runtime."

    //Decimal to char conversion is also not supported.
    try
        let charVal = Convert.ToChar decimalVal
        ()
    with :? InvalidCastException ->
        printfn "Decimal-to-Char conversion is not supported by the .NET Runtime."

Public Sub ConvertCharDecimal(ByVal charVal As Char)
    Dim decimalVal As [Decimal] = 0

    ' Char to decimal conversion is not supported and will always
    ' throw an InvalidCastException.
    Try
        decimalVal = System.Convert.ToDecimal(charVal)
    Catch exception As System.InvalidCastException
        System.Console.WriteLine( _
             "Char-to-Decimal conversion is not supported " + _
             "by the .NET Framework.")
    End Try

    'Decimal to char conversion is also not supported.
    Try
        charVal = System.Convert.ToChar(decimalVal)
    Catch exception As System.InvalidCastException
        System.Console.WriteLine( _
            "Decimal-to-Char conversion is not supported " + _
            "by the .NET Framework.")
    End Try
End Sub

適用於

ToChar(DateTime)

來源:: Convert.cs

來源:: Convert.cs

來源:: Convert.cs

來源:: Convert.cs

來源:: Convert.cs

呼叫此方法總是拋 InvalidCastException出。

public:
 static char ToChar(DateTime value);

public static char ToChar(DateTime value);

static member ToChar : DateTime -> char

Public Shared Function ToChar (value As DateTime) As Char

參數

value: DateTime

轉換的日期和時間值。

傳回

Char

此轉換不被支援。沒有任何價值回傳。

例外狀況

InvalidCastException

此轉換不被支援。

適用於

ToChar(Char)

來源:: Convert.cs

來源:: Convert.cs

來源:: Convert.cs

來源:: Convert.cs

來源:: Convert.cs

回傳指定的 Unicode 字元值;並未進行實際的轉換。

public:
 static char ToChar(char value);

public static char ToChar(char value);

static member ToChar : char -> char

Public Shared Function ToChar (value As Char) As Char

參數

value: Char

Unicode 字元要回傳。

傳回

Char

value 未改變地返回。

適用於

ToChar(Byte)

來源:: Convert.cs

來源:: Convert.cs

來源:: Convert.cs

來源:: Convert.cs

來源:: Convert.cs

將指定 8 位元無符號整數的值轉換為其等效的 Unicode 字元。

public:
 static char ToChar(System::Byte value);

public static char ToChar(byte value);

static member ToChar : byte -> char

Public Shared Function ToChar (value As Byte) As Char

參數

value: Byte

要轉換的是 8 位元無符號整數。

傳回

Char

一個等價 value於的 Unicode 字元。

範例

以下範例將一組無符號位元組 Char 轉換為數值。

byte[] bytes = {Byte.MinValue, 40, 80, 120, 180, Byte.MaxValue};
char result;
foreach (byte number in bytes)
{
   result = Convert.ToChar(number);
   Console.WriteLine("{0} converts to '{1}'.", number, result);
}
// The example displays the following output:
//       0 converts to ' '.
//       40 converts to '('.
//       80 converts to 'P'.
//       120 converts to 'x'.
//       180 converts to '''.
//       255 converts to 'ÿ'.

let bytes = 
    [| Byte.MinValue; 40uy; 80uy; 120uy; 180uy; Byte.MaxValue|]
for number in bytes do
    let result = Convert.ToChar number
    printfn $"{number} converts to '{result}'." 
// The example displays the following output:
//       0 converts to ' '.
//       40 converts to '('.
//       80 converts to 'P'.
//       120 converts to 'x'.
//       180 converts to '''.
//       255 converts to 'ÿ'.

Dim bytes() As Byte = {Byte.MinValue, 40, 80, 120, 180, Byte.MaxValue}
Dim result As Char
For Each number As Byte In bytes
   result = Convert.ToChar(number)
   Console.WriteLine("{0} converts to '{1}'.", number, result)
Next
' The example displays the following output:
'       0 converts to ' '.
'       40 converts to '('.
'       80 converts to 'P'.
'       120 converts to 'x'.
'       180 converts to '''.
'       255 converts to 'ÿ'.

適用於

ToChar(Boolean)

來源:: Convert.cs

來源:: Convert.cs

來源:: Convert.cs

來源:: Convert.cs

來源:: Convert.cs

呼叫此方法總是拋 InvalidCastException出。

public:
 static char ToChar(bool value);

public static char ToChar(bool value);

static member ToChar : bool -> char

Public Shared Function ToChar (value As Boolean) As Char

參數

value: Boolean

轉換時的布林值。

傳回

Char

此轉換不被支援。沒有任何價值回傳。

例外狀況

InvalidCastException

此轉換不被支援。

適用於

ToChar(Int32)

來源:: Convert.cs

來源:: Convert.cs

來源:: Convert.cs

來源:: Convert.cs

來源:: Convert.cs

將指定的 32 位元有號整數值轉換為其等效的 Unicode 字元。

public:
 static char ToChar(int value);

public static char ToChar(int value);

static member ToChar : int -> char

Public Shared Function ToChar (value As Integer) As Char

參數

value: Int32

要轉換的32位帶正負號整數。

傳回

Char

一個等價 value於的 Unicode 字元。

例外狀況

OverflowException

value 小於 Char.MinValue 或大於 Char.MaxValue。

範例

以下範例將一組有符號整數陣列轉換為 Char 數值。

int[] numbers = { -1, 0, 40, 160, 255, 1028,
                  2011, 30001, 207154, Int32.MaxValue };
char result;
foreach (int number in numbers)
{
   try {
      result = Convert.ToChar(number);
      Console.WriteLine("{0} converts to '{1}'.", number, result);
   }
   catch (OverflowException) {
      Console.WriteLine("{0} is outside the range of the Char data type.",
                        number);
   }
}
//       -1 is outside the range of the Char data type.
//       0 converts to ' '.
//       40 converts to '('.
//       160 converts to ' '.
//       255 converts to 'ÿ'.
//       1028 converts to 'Є'.
//       2011 converts to 'ߛ'.
//       30001 converts to '由'.
//       207154 is outside the range of the Char data type.
//       2147483647 is outside the range of the Char data type.

let numbers = 
    [| -1; 0; 40; 160; 255; 1028; 2011
       30001; 207154; Int32.MaxValue |]
for number in numbers do
    try
        let result = Convert.ToChar number
        printfn $"{number} converts to '{result}'." 
    with :? OverflowException ->
        printfn $"{number} is outside the range of the Char data type."
//       -1 is outside the range of the Char data type.
//       0 converts to ' '.
//       40 converts to '('.
//       160 converts to ' '.
//       255 converts to 'ÿ'.
//       1028 converts to 'Є'.
//       2011 converts to 'ߛ'.
//       30001 converts to '由'.
//       207154 is outside the range of the Char data type.
//       2147483647 is outside the range of the Char data type.

Dim numbers() As Integer = { -1, 0, 40, 160, 255, 1028, _
                           2011, 30001, 207154, Int32.MaxValue }
Dim result As Char
For Each number As Integer In numbers
   Try
      result = Convert.ToChar(number)
      Console.WriteLine("{0} converts to '{1}'.", number, result)
   Catch e As OverflowException
      Console.WriteLine("{0} is outside the range of the Char data type.", _
                        number)
   End Try
Next
'       -1 is outside the range of the Char data type.
'       0 converts to ' '.
'       40 converts to '('.
'       160 converts to ' '.
'       255 converts to 'ÿ'.
'       1028 converts to 'Є'.
'       2011 converts to 'ߛ'.
'       30001 converts to '由'.
'       207154 is outside the range of the Char data type.
'       2147483647 is outside the range of the Char data type.

適用於

意見反應

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