UTF8Encoding 建構函式

public:
 UTF8Encoding();

public UTF8Encoding();

Public Sub New ()

範例

以下範例會建立一個新 UTF8Encoding 實例並顯示其名稱。

using System;
using System.Text;

class UTF8EncodingExample {
    public static void Main() {
        UTF8Encoding utf8 = new UTF8Encoding();
        String encodingName = utf8.EncodingName;
        Console.WriteLine("Encoding name: " + encodingName);
    }
}

Imports System.Text

Class UTF8EncodingExample
    
    Public Shared Sub Main()
        Dim utf8 As New UTF8Encoding()
        Dim encodingName As String = utf8.EncodingName
        Console.WriteLine("Encoding name: " & encodingName)
    End Sub
End Class

備註

此建構子建立一個不提供 Unicode 位元組順序標記的實例，且在偵測到無效編碼時不會拋出例外。

另請參閱

• GetPreamble()

public:
 UTF8Encoding(bool encoderShouldEmitUTF8Identifier);

public UTF8Encoding(bool encoderShouldEmitUTF8Identifier);

new System.Text.UTF8Encoding : bool -> System.Text.UTF8Encoding

Public Sub New (encoderShouldEmitUTF8Identifier As Boolean)

參數

範例

以下範例建立一個新 UTF8Encoding 實例，並指定該方法應 GetPreamble 輸出 Unicode 位元組順序標記前綴。 接著，該 GetPreamble 方法會回傳 Unicode 位元組順序標記的前綴。

using System;
using System.Text;

class UTF8EncodingExample {
    public static void Main() {
        UTF8Encoding utf8 = new UTF8Encoding();
        UTF8Encoding utf8EmitBOM = new UTF8Encoding(true);

        Console.WriteLine("utf8 preamble:");
        ShowArray(utf8.GetPreamble());

        Console.WriteLine("utf8EmitBOM:");
        ShowArray(utf8EmitBOM.GetPreamble());
    }

    public static void ShowArray(Array theArray) {
        foreach (Object o in theArray) {
            Console.Write("[{0}]", o);
        }
        Console.WriteLine();
    }
}

Imports System.Text

Class UTF8EncodingExample
    
    Public Shared Sub Main()
        Dim utf8 As New UTF8Encoding()
        Dim utf8EmitBOM As New UTF8Encoding(True)
        
        Console.WriteLine("utf8 preamble:")
        ShowArray(utf8.GetPreamble())
        
        Console.WriteLine("utf8EmitBOM:")
        ShowArray(utf8EmitBOM.GetPreamble())
    End Sub
    
    
    Public Shared Sub ShowArray(theArray As Array)
        Dim o As Object
        For Each o In  theArray
            Console.Write("[{0}]", o)
        Next o
        Console.WriteLine()
    End Sub
End Class

備註

此建構子建立一個實例，當偵測到無效編碼時不會拋出例外。

參數 encoderShouldEmitUTF8Identifier 控制方法的 GetPreamble 運作。 若 true，該方法會回傳包含 Unicode 位元組順序標記（BOM）的位元組陣列，格式為 UTF-8。 若 false，則回傳一個零長度的位元組陣列。 然而，設定 encoderShouldEmitUTF8Identifier 為 true 並不會使 GetBytes 方法在位元組陣列開頭加上 BOM，也不會將 GetByteCount BOM 中的位元組數納入位元組計數。

另請參閱

• GetPreamble()

public:
 UTF8Encoding(bool encoderShouldEmitUTF8Identifier, bool throwOnInvalidBytes);

public UTF8Encoding(bool encoderShouldEmitUTF8Identifier, bool throwOnInvalidBytes);

new System.Text.UTF8Encoding : bool * bool -> System.Text.UTF8Encoding

Public Sub New (encoderShouldEmitUTF8Identifier As Boolean, throwOnInvalidBytes As Boolean)

參數

範例

以下範例建立一個新 UTF8Encoding 實例，指定 GetPreamble 該方法不應發出 Unicode 位元組順序標記前綴，且當偵測到無效編碼時應拋出例外。 此建構子的行為會與預設 UTF8Encoding() 建構子比較，後者在偵測到無效編碼時不會拋出例外。 這兩個 UTF8Encoding 實例編碼了一個字元陣列，該陣列中包含兩個高代詞（U+D801 和 U+D802），這是無效的字元序列;高代詞後應總是緊接著低代詞。

using System;
using System.Text;

class Example
{
    public static void Main()
    {
        UTF8Encoding utf8 = new UTF8Encoding();
        UTF8Encoding utf8ThrowException = new UTF8Encoding(false, true);

        // Create an array with two high surrogates in a row (\uD801, \uD802).
        Char[] chars = new Char[] {'a', 'b', 'c', '\uD801', '\uD802', 'd'};

        // The following method call will not throw an exception.
        Byte[] bytes = utf8.GetBytes(chars);
        ShowArray(bytes);
        Console.WriteLine();

        try {
            // The following method call will throw an exception.
            bytes = utf8ThrowException.GetBytes(chars);
            ShowArray(bytes);
        }
        catch (EncoderFallbackException e) {
            Console.WriteLine("{0} exception\nMessage:\n{1}",
                              e.GetType().Name, e.Message);
        }
    }

    public static void ShowArray(Array theArray) {
        foreach (Object o in theArray)
            Console.Write("{0:X2} ", o);

        Console.WriteLine();
    }
}
// The example displays the following output:
//    61 62 63 EF BF BD EF BF BD 64
//
//    EncoderFallbackException exception
//    Message:
//    Unable to translate Unicode character \uD801 at index 3 to specified code page.

Imports System.Text

Class Example
    Public Shared Sub Main()
        Dim utf8 As New UTF8Encoding()
        Dim utf8ThrowException As New UTF8Encoding(False, True)
        
        ' Create an array with two high surrogates in a row (\uD801, \uD802).
        Dim chars() As Char = {"a"c, "b"c, "c"c, ChrW(&hD801), ChrW(&hD802), "d"c}
        
        ' The following method call will not throw an exception.
        Dim bytes As Byte() = utf8.GetBytes(chars)
        ShowArray(bytes)
        Console.WriteLine()
        
        Try
            ' The following method call will throw an exception.
            bytes = utf8ThrowException.GetBytes(chars)
            ShowArray(bytes)
        Catch e As EncoderFallbackException
            Console.WriteLine("{0} exception{2}Message:{2}{1}",
                              e.GetType().Name, e.Message, vbCrLf)
        End Try
    End Sub
    
    
    Public Shared Sub ShowArray(theArray As Array)
        For Each o In theArray
            Console.Write("{0:X2} ", o)
        Next
        Console.WriteLine()
    End Sub
End Class
' The example displays the following output:
'    61 62 63 EF BF BD EF BF BD 64
'
'    EncoderFallbackException exception
'    Message:
'    Unable to translate Unicode character \uD801 at index 3 to specified code page.

備註

參數 encoderShouldEmitUTF8Identifier 控制方法的 GetPreamble 運作。 若 true，該方法會回傳包含 Unicode 位元組順序標記（BOM）的位元組陣列，格式為 UTF-8。 若 false，則回傳一個零長度的位元組陣列。 然而，設定 encoderShouldEmitUTF8Identifier 為 true 並不會使 GetBytes 方法在位元組陣列開頭加上 BOM，也不會將 GetByteCount BOM 中的位元組數納入位元組計數。

若 throwOnInvalidBytes ， true偵測無效位元組序列的方法會 System.ArgumentException 拋出例外。 否則，方法不會拋出例外，且無效序列會被忽略。

另請參閱

• GetPreamble()