DynamicObject.TryInvokeMember(InvokeMemberBinder, Object[], Object) 方法

public:
 virtual bool TryInvokeMember(System::Dynamic::InvokeMemberBinder ^ binder, cli::array <System::Object ^> ^ args, [Runtime::InteropServices::Out] System::Object ^ % result);

public virtual bool TryInvokeMember(System.Dynamic.InvokeMemberBinder binder, object[] args, out object result);

public virtual bool TryInvokeMember(System.Dynamic.InvokeMemberBinder binder, object?[]? args, out object? result);

abstract member TryInvokeMember : System.Dynamic.InvokeMemberBinder * obj[] * obj -> bool
override this.TryInvokeMember : System.Dynamic.InvokeMemberBinder * obj[] * obj -> bool

Public Overridable Function TryInvokeMember (binder As InvokeMemberBinder, args As Object(), ByRef result As Object) As Boolean

參數

傳回

如果作業成功，則為 true，否則為 false。 若此方法回傳 false，該語言的執行時綁定器決定行為。 （大多數情況下會拋出語言特定的執行時例外。）

範例

假設你想提供替代語法來存取字典中的值，這樣你就不用寫 sampleDictionary["Text"] = "Sample text"（Visual Basic 中的 sampleDictionary("Text") = "Sample text"），而是寫成 sampleDictionary.Text = "Sample text"。 此外，你也希望能調用這本字典上所有標準的字典方法。

以下程式碼範例展示了 DynamicDictionary 由該 DynamicObject 類別衍生而來的類別。 DynamicDictionary 類別包含一個 Dictionary<string, object> 型別的物件（Visual Basic 中的 Dictionary(Of String, Object)）用來儲存鍵值對。 它會覆 TryInvokeMember 寫支援 Dictionary<TKey,TValue> 類別的方法，並覆寫 TrySetMember 與 TryGetMember 方法以支援新的語法。 它也提供一種 Print 方法，可以列印所有字典的鍵與值。

// Add using System.Reflection;
// to the beginning of the file.

// The class derived from DynamicObject.
public class DynamicDictionary : DynamicObject
{
    // The inner dictionary.
    Dictionary<string, object> dictionary
        = new Dictionary<string, object>();

    // Getting a property.
    public override bool TryGetMember(
        GetMemberBinder binder, out object result)
    {
        return dictionary.TryGetValue(binder.Name, out result);
    }

    // Setting a property.
    public override bool TrySetMember(
        SetMemberBinder binder, object value)
    {
        dictionary[binder.Name] = value;
        return true;
    }

    // Calling a method.
    public override bool TryInvokeMember(
        InvokeMemberBinder binder, object[] args, out object result)
    {
        Type dictType = typeof(Dictionary<string, object>);
        try
        {
            result = dictType.InvokeMember(
                         binder.Name,
                         BindingFlags.InvokeMethod,
                         null, dictionary, args);
            return true;
        }
        catch
        {
            result = null;
            return false;
        }
    }

    // This methods prints out dictionary elements.
    public void Print()
    {
        foreach (var pair in dictionary)
            Console.WriteLine(pair.Key + " " + pair.Value);
        if (dictionary.Count == 0)
            Console.WriteLine("No elements in the dictionary.");
    }
}

class Program
{
    static void Main(string[] args)
    {
        // Creating a dynamic dictionary.
        dynamic person = new DynamicDictionary();

        // Adding new dynamic properties.
        // The TrySetMember method is called.
        person.FirstName = "Ellen";
        person.LastName = "Adams";

        // Calling a method defined in the DynmaicDictionary class.
        // The Print method is called.
        person.Print();

        Console.WriteLine(
            "Removing all the elements from the dictionary.");

        // Calling a method that is not defined in the DynamicDictionary class.
        // The TryInvokeMember method is called.
        person.Clear();

        // Calling the Print method again.
        person.Print();

        // The following statement throws an exception at run time.
        // There is no Sample method
        // in the dictionary or in the DynamicDictionary class.
        // person.Sample();
    }
}

// This example has the following output:

// FirstName Ellen
// LastName Adams
// Removing all the elements from the dictionary.
// No elements in the dictionary.

' Add Imports System.Reflection
' to the beginning of the file.

' The class derived from DynamicObject.
Public Class DynamicDictionary
    Inherits DynamicObject

    ' The inner dictionary.
    Dim dictionary As New Dictionary(Of String, Object)

    ' Getting a property value.
    Public Overrides Function TryGetMember(
        ByVal binder As System.Dynamic.GetMemberBinder,
        ByRef result As Object) As Boolean

        Return dictionary.TryGetValue(binder.Name, result)
    End Function

    ' Setting a property value.
    Public Overrides Function TrySetMember(
        ByVal binder As System.Dynamic.SetMemberBinder,
        ByVal value As Object) As Boolean

        dictionary(binder.Name) = value
        Return True
    End Function


    ' Calling a method.
    Public Overrides Function TryInvokeMember(
        ByVal binder As System.Dynamic.InvokeMemberBinder,
        ByVal args() As Object, ByRef result As Object) As Boolean

        Dim dictType As Type = GetType(Dictionary(Of String, Object))
        Try
            result = dictType.InvokeMember(
                         binder.Name,
                         BindingFlags.InvokeMethod,
                         Nothing, dictionary, args)
            Return True
        Catch ex As Exception
            result = Nothing
            Return False
        End Try
    End Function

    ' This method prints out dictionary elements.
    Public Sub Print()
        For Each pair In dictionary
            Console.WriteLine(pair.Key & " " & pair.Value)
        Next
        If (dictionary.Count = 0) Then
            Console.WriteLine("No elements in the dictionary.")
        End If
    End Sub
End Class

Sub Test()
    ' Creating a dynamic dictionary.
    Dim person As Object = New DynamicDictionary()

    ' Adding new dynamic properties.
    ' The TrySetMember method is called.
    person.FirstName = "Ellen"
    person.LastName = "Adams"

    ' Calling a method defined in the DynmaicDictionary class.
    ' The Print method is called.
    person.Print()

    Console.WriteLine(
        "Removing all the elements from the dictionary.")

    ' Calling a method that is not defined in the DynamicDictionary class.
    ' The TryInvokeMember method is called.
    person.Clear()

    ' Calling the Print method again.
    person.Print()

    ' The following statement throws an exception at run time.
    ' There is no Sample method 
    ' in the dictionary or in the DynamicDictionary class.
    ' person.Sample()
End Sub


' This example has the following output:

' FirstName Ellen 
' LastName Adams
' Removing all the elements from the dictionary.
' No elements in the dictionary.

備註

從該 DynamicObject 類別衍生的類別可以覆寫此方法，指定如何對動態物件執行呼叫物件成員的操作。 當方法未被覆寫時，語言的執行時綁定器決定行為。 （大多數情況下會拋出語言特定的執行時例外。）

若此方法被覆寫，執行如 sampleObject.SampleMethod(100)，其中 sampleObject 是從 DynamicObject 類別衍生出的操作，該方法會自動被呼叫。

你也可以在從該 DynamicObject 類別衍生出來的類別中加入自己的方法。 例如，如果你覆寫該方法， TryInvokeMember 動態派遣系統會先嘗試判斷該指定方法是否存在於該類別中。 如果找不到該方法，則使用該 TryInvokeMember 實作。

此方法不支援 ref 參數 out 。 陣列中 args 的所有參數皆以值傳遞。