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MulticastDelegate-Klasse

  • Artikel

Stellt einen Multicastdelegaten dar, d. h. einen Delegaten, in dessen Aufrufliste sich mehrere Elemente befinden können.

Namespace: System
Assembly: mscorlib (in mscorlib.dll)

Syntax

'Declaration
<SerializableAttribute> _
<ComVisibleAttribute(True)> _
Public MustInherit Class MulticastDelegate
    Inherits Delegate
'Usage
Dim instance As MulticastDelegate

[SerializableAttribute] 
[ComVisibleAttribute(true)] 
public abstract class MulticastDelegate : Delegate

[SerializableAttribute] 
[ComVisibleAttribute(true)] 
public ref class MulticastDelegate abstract : public Delegate

/** @attribute SerializableAttribute() */ 
/** @attribute ComVisibleAttribute(true) */ 
public abstract class MulticastDelegate extends Delegate

SerializableAttribute 
ComVisibleAttribute(true) 
public abstract class MulticastDelegate extends Delegate

Hinweise

MulticastDelegate ist eine besondere Klasse. Compiler und andere Tools können von dieser Klasse ableiten, es ist aber nicht möglich, explizit von ihr abzuleiten. Das gleiche gilt für die Delegate-Klasse.

Ein MulticastDelegate verfügt über eine aus einem oder mehreren Elementen bestehende verkettete Liste von Delegaten, die als Aufrufliste bezeichnet wird. Wenn ein Multicastdelegat aufgerufen wird, werden die Delegaten in der Reihenfolge synchron aufgerufen, in der sie in der Liste aufgeführt sind. Wenn bei der Ausführung der Liste ein Fehler auftritt, wird eine Ausnahme ausgelöst.

Beispiel

Das folgende Beispiel veranschaulicht die Verwendung einer von MulticastDelegate abgeleiteten Klasse.

Imports System
Imports Microsoft.VisualBasic

' This class contains strings. It has a member method that
' accepts a multicast delegate as a parameter and calls it

Class HoldsStrings

    ' The following line causes the compiler to generate
    ' a new delegate class named CheckAndPrintDelegate that
    ' inherits from System.MulticastDelegate.
    Delegate Sub CheckAndPrintDelegate(ByVal str As String)

    ' An ArrayList that holds strings
    Private myStringArray As New System.Collections.ArrayList()

    Public Sub addstring(ByVal str As String)
        myStringArray.Add(str)
    End Sub 'addstring

    ' Iterate through the strings and invoke the method(s) that the delegate points to
    Public Sub PrintAllQualified(ByVal myDelegate As CheckAndPrintDelegate)
        Dim str As String
        For Each str In myStringArray
            myDelegate(str)
        Next str
    End Sub 'PrintAllQualified

End Class     'end of class HoldsStrings

' This class contains a few sample methods
Class StringFuncs
    ' This method prints a string that it is passed if the string starts with a vowel
    Public Shared Sub ConStart(ByVal str As String)
        If Not (str.Chars(0) = "a"c Or str.Chars(0) = "e"c Or str.Chars(0) = "i"c Or str.Chars(0) = "o"c Or str.Chars(0) = "u"c) Then
            Console.WriteLine(str)
        End If
    End Sub 'ConStart

    ' This method prints a string that it is passed if the string starts with a consonant
    Public Shared Sub VowelStart(ByVal str As String)
        If (str.Chars(0) = "a"c Or str.Chars(0) = "e"c Or str.Chars(0) = "i"c Or str.Chars(0) = "o"c Or str.Chars(0) = "u"c) Then
            Console.WriteLine(str)
        End If
    End Sub 'VowelStart
End Class 'StringFuncs

' This class demonstrates using Delegates, including using the Remove and
' Combine methods to create and modify delegate combinations.
Class Test

    Public Shared Sub Main()
        ' Declare the HoldsStrings class and add some strings
        Dim myHoldsStrings As New HoldsStrings()
        myHoldsStrings.addstring("this")
        myHoldsStrings.addstring("is")
        myHoldsStrings.addstring("a")
        myHoldsStrings.addstring("multicast")
        myHoldsStrings.addstring("delegate")
        myHoldsStrings.addstring("example")

        ' Create two delegates individually using different methods
        Dim ConStartDel = New HoldsStrings.CheckAndPrintDelegate(AddressOf StringFuncs.ConStart)

        Dim VowStartDel As New HoldsStrings.CheckAndPrintDelegate(AddressOf StringFuncs.VowelStart)

        ' Demonstrate that MulticastDelegates may store only one delegate
        Dim DelegateList() As [Delegate]

        ' Returns an array of all delegates stored in the linked list of the
        ' MulticastDelegate. In these cases the lists will hold only one (Multicast) delegate
        DelegateList = ConStartDel.GetInvocationList()
        Console.WriteLine("ConStartDel contains " + DelegateList.Length.ToString() + " delegate(s).")

        DelegateList = VowStartDel.GetInvocationList()
        Console.WriteLine(("ConStartVow contains " + DelegateList.Length.ToString() + " delegate(s)."))

        ' Determine whether the delegates are System.Multicast delegates
        If TypeOf ConStartDel Is System.MulticastDelegate And TypeOf VowStartDel Is System.MulticastDelegate Then
            Console.WriteLine("ConStartDel and ConStartVow are System.MulticastDelegates")
        End If

        ' Run the two single delegates one after the other
        Console.WriteLine("Running ConStartDel delegate:")
        myHoldsStrings.PrintAllQualified(ConStartDel)
        Console.WriteLine("Running VowStartDel delegate:")
        myHoldsStrings.PrintAllQualified(VowStartDel)

        ' Create a new, empty MulticastDelegate
        Dim MultiDel As HoldsStrings.CheckAndPrintDelegate

        ' Delegate.Combine receives an unspecified number of MulticastDelegates as parameters
        MultiDel = CType([Delegate].Combine(ConStartDel, VowStartDel), HoldsStrings.CheckAndPrintDelegate)

        ' How many delegates is this delegate holding?
        DelegateList = MultiDel.GetInvocationList()
        Console.WriteLine((ControlChars.Cr + "MulitDel contains " + DelegateList.Length.ToString() + " delegates."))

        ' What happens when this mulitcast delegate is passed to PrintAllQualified
        Console.WriteLine("Running the multiple delegate that combined the first two")
        myHoldsStrings.PrintAllQualified(MultiDel)

        ' The Remove and Combine methods modify the multiple delegate
        MultiDel = CType([Delegate].Remove(MultiDel, VowStartDel), HoldsStrings.CheckAndPrintDelegate)
        MultiDel = CType([Delegate].Combine(MultiDel, ConStartDel), HoldsStrings.CheckAndPrintDelegate)

        ' Finally, pass the combined delegates to PrintAllQualified again
        Console.WriteLine(ControlChars.Cr + "Running the multiple delegate that contains two copies of ConStartDel:")
        myHoldsStrings.PrintAllQualified(MultiDel)

        Return
    End Sub 'end of main
End Class 'end of Test

using System;

    // This class contains strings. It has a member method that
    // accepts a multicast delegate as a parameter and calls it.

    class HoldsStrings
    {
        // The following line causes the compiler to generate
        // a new delegate class named CheckAndPrintDelegate that
        // inherits from System.MulticastDelegate.
        public delegate void CheckAndPrintDelegate(string str);

        // An ArrayList that holds strings
        private System.Collections.ArrayList myStringArray = new System.Collections.ArrayList();

        // A method that adds more strings to the Collection
        public void addstring( string str) {
            myStringArray.Add(str);
        }

        // Iterate through the strings and invoke the method(s) that the delegate points to
        public void PrintAllQualified(CheckAndPrintDelegate myDelegate) {
            foreach (string str in myStringArray) {
                myDelegate(str);
            }
        }
    }   //end of class HoldsStrings

    // This class contains a few sample methods
    class StringFuncs
    {
        // This method prints a string that it is passed if the string starts with a vowel
        public static void ConStart(string str) {
            if (!(str[0]=='a'||str[0]=='e'||str[0]=='i'||str[0]=='o'||str[0]=='u'))
                Console.WriteLine(str);
        }

        // This method prints a string that it is passed if the string starts with a consonant
        public static void VowelStart(string str) {
            if ((str[0]=='a'||str[0]=='e'||str[0]=='i'||str[0]=='o'||str[0]=='u'))
                Console.WriteLine(str);
        }
    }

    // This class demonstrates using Delegates, including using the Remove and
    // Combine methods to create and modify delegate combinations.
    class Test
    {
        static public void Main()
        {
            // Declare the HoldsStrings class and add some strings
            HoldsStrings myHoldsStrings = new HoldsStrings();
            myHoldsStrings.addstring("This");
            myHoldsStrings.addstring("is");
            myHoldsStrings.addstring("a");
            myHoldsStrings.addstring("multicast");
            myHoldsStrings.addstring("delegate");
            myHoldsStrings.addstring("example");

            // Create two delegates individually using different methods
            HoldsStrings.CheckAndPrintDelegate ConStartDel =
                new HoldsStrings.CheckAndPrintDelegate(StringFuncs.ConStart);
            HoldsStrings.CheckAndPrintDelegate VowStartDel =
                new HoldsStrings.CheckAndPrintDelegate(StringFuncs.VowelStart);

            // Demonstrate that MulticastDelegates may store only one delegate
            Delegate [] DelegateList;

            // Returns an array of all delegates stored in the linked list of the
            // MulticastDelegate. In these cases the lists will hold only one (Multicast) delegate
            DelegateList = ConStartDel.GetInvocationList();
            Console.WriteLine("ConStartDel contains " + DelegateList.Length + " delegate(s).");
            DelegateList = VowStartDel.GetInvocationList();
            Console.WriteLine("ConStartVow contains " + DelegateList.Length + " delegate(s).");

            // Determine whether the delegates are System.Multicast delegates
            // if (ConStartDel is System.MulticastDelegate && VowStartDel is System.MulticastDelegate) {
                Console.WriteLine("ConStartDel and ConStartVow are System.MulticastDelegates");
            // }

            // Run the two single delegates one after the other
            Console.WriteLine("Running ConStartDel delegate:");
            myHoldsStrings.PrintAllQualified(ConStartDel);
            Console.WriteLine("Running VowStartDel delegate:");
            myHoldsStrings.PrintAllQualified(VowStartDel);

            // Create a new, empty MulticastDelegate
            HoldsStrings.CheckAndPrintDelegate MultiDel;

            // Delegate.Combine receives an unspecified number of MulticastDelegates as parameters
            MultiDel = (HoldsStrings.CheckAndPrintDelegate) Delegate.Combine(ConStartDel, VowStartDel);

            // How many delegates is this delegate holding?
            DelegateList = MultiDel.GetInvocationList();
            Console.WriteLine("\nMulitDel contains " + DelegateList.Length + " delegates.");

            // What happens when this mulitcast delegate is passed to PrintAllQualified
            Console.WriteLine("Running the multiple delegate that combined the first two");
            myHoldsStrings.PrintAllQualified(MultiDel);

            // The Remove and Combine methods modify the multiple delegate
            MultiDel = (HoldsStrings.CheckAndPrintDelegate) Delegate.Remove(MultiDel, VowStartDel);
            MultiDel = (HoldsStrings.CheckAndPrintDelegate) Delegate.Combine(MultiDel, ConStartDel);

            // Finally, pass the combined delegates to PrintAllQualified again
            Console.WriteLine("\nRunning the multiple delegate that contains two copies of ConStartDel:");
            myHoldsStrings.PrintAllQualified(MultiDel);

            return;
        }   //end of main
    }   //end of Test

using namespace System;

// This class contains strings. It has a member method that
// accepts a multicast delegate as a parameter and calls it.
ref class HoldsStrings
{
public:
   // The following line causes the compiler to generate
   // a new delegate class named CheckAndPrintDelegate that
   // inherits from System.MulticastDelegate.
   delegate void CheckAndPrintDelegate( String^ str );

private:

   // An ArrayList that holds strings
   System::Collections::ArrayList^ myStringArray;

public:
   HoldsStrings()
   {
      myStringArray = gcnew System::Collections::ArrayList;
   }

   // A method that adds more strings to the Collection
   void addstring( String^ str )
   {
      myStringArray->Add( str );
   }


   // Iterate through the strings and invoke the method(s) that the delegate points to
   void PrintAllQualified( CheckAndPrintDelegate^ myDelegate )
   {
      System::Collections::IEnumerator^ myEnum = myStringArray->GetEnumerator();
      while ( myEnum->MoveNext() )
      {
         String^ str = safe_cast<String^>(myEnum->Current);
         myDelegate( str );
      }
   }

};

//end of class HoldsStrings
// This class contains a few sample methods
ref class StringFuncs
{
public:

   // This method prints a String* that it is passed if the String* starts with a vowel
   static void ConStart( String^ str )
   {
      if (  !(str[ 0 ] == 'a' || str[ 0 ] == 'e' || str[ 0 ] == 'i' || str[ 0 ] == 'o' || str[ 0 ] == 'u') )
            Console::WriteLine( str );
   }

   // This method prints a String* that it is passed if the String* starts with a consonant
   static void VowelStart( String^ str )
   {
      if ( (str[ 0 ] == 'a' || str[ 0 ] == 'e' || str[ 0 ] == 'i' || str[ 0 ] == 'o' || str[ 0 ] == 'u') )
            Console::WriteLine( str );
   }
};

// This function demonstrates using Delegates, including using the Remove and
// Combine methods to create and modify delegate combinations.
int main()
{
   // Declare the HoldsStrings class and add some strings
   HoldsStrings^ myHoldsStrings = gcnew HoldsStrings;
   myHoldsStrings->addstring( "This" );
   myHoldsStrings->addstring( "is" );
   myHoldsStrings->addstring( "a" );
   myHoldsStrings->addstring( "multicast" );
   myHoldsStrings->addstring( "delegate" );
   myHoldsStrings->addstring( "example" );

   // Create two delegates individually using different methods
   HoldsStrings::CheckAndPrintDelegate^ ConStartDel = gcnew HoldsStrings::CheckAndPrintDelegate( StringFuncs::ConStart );
   HoldsStrings::CheckAndPrintDelegate^ VowStartDel = gcnew HoldsStrings::CheckAndPrintDelegate( StringFuncs::VowelStart );

   // Demonstrate that MulticastDelegates may store only one delegate
   array<Delegate^>^DelegateList;

   // Returns an array of all delegates stored in the linked list of the
   // MulticastDelegate. In these cases the lists will hold only one (Multicast) delegate
   DelegateList = ConStartDel->GetInvocationList();
   Console::WriteLine( "ConStartDel contains {0} delegate(s).", DelegateList->Length );
   DelegateList = VowStartDel->GetInvocationList();
   Console::WriteLine( "ConStartVow contains {0} delegate(s).", DelegateList->Length );

   // Determine whether the delegates are System::Multicast delegates
   if ( dynamic_cast<System::MulticastDelegate^>(ConStartDel) && dynamic_cast<System::MulticastDelegate^>(VowStartDel) )
   {
      Console::WriteLine( "ConStartDel and ConStartVow are System::MulticastDelegates" );
   }

   // Run the two single delegates one after the other
   Console::WriteLine( "Running ConStartDel delegate:" );
   myHoldsStrings->PrintAllQualified( ConStartDel );
   Console::WriteLine( "Running VowStartDel delegate:" );
   myHoldsStrings->PrintAllQualified( VowStartDel );

   // Create a new, empty MulticastDelegate
   HoldsStrings::CheckAndPrintDelegate^ MultiDel;

   // Delegate::Combine receives an unspecified number of MulticastDelegates as parameters
   MultiDel = dynamic_cast<HoldsStrings::CheckAndPrintDelegate^>(Delegate::Combine( ConStartDel, VowStartDel ));

   // How many delegates is this delegate holding?
   DelegateList = MultiDel->GetInvocationList();
   Console::WriteLine( "\nMulitDel contains {0} delegates.", DelegateList->Length );

   // What happens when this mulitcast delegate is passed to PrintAllQualified
   Console::WriteLine( "Running the multiple delegate that combined the first two" );
   myHoldsStrings->PrintAllQualified( MultiDel );

   // The Remove and Combine methods modify the multiple delegate
   MultiDel = dynamic_cast<HoldsStrings::CheckAndPrintDelegate^>(Delegate::Remove( MultiDel, VowStartDel ));
   MultiDel = dynamic_cast<HoldsStrings::CheckAndPrintDelegate^>(Delegate::Combine( MultiDel, ConStartDel ));

   // Finally, pass the combined delegates to PrintAllQualified again
   Console::WriteLine( "\nRunning the multiple delegate that contains two copies of ConStartDel:" );
   myHoldsStrings->PrintAllQualified( MultiDel );
} //end of main

import System.*;

// This class contains strings. It has a member method that
// accepts a multicast delegate as a parameter and calls it.

class HoldsStrings
{
    /** @delegate
     */

    // This delegate is declared as a void, so the compiler automatically
    // generates a new class, named CheckAndPrintDelegate, that inherits from
    // System.MulticastDelegate.
    public delegate void CheckAndPrintDelegate(String str);

    // An ArrayList that holds strings
    private System.Collections.ArrayList myStringArray =
        new System.Collections.ArrayList();

    // A method that adds more strings to the Collection
    public void addstring(String str)
    {
        myStringArray.Add(str);
    } //addstring

    // Iterate through the strings and invoke the method(s) that the delegate
    // points to
    public void PrintAllQualified(CheckAndPrintDelegate myDelegate)
    {
        for (int iCtr1 = 0; iCtr1 < myStringArray.get_Count(); iCtr1++) {
            String str = System.Convert.ToString(myStringArray.get_Item(iCtr1));
            myDelegate.Invoke(str);
        }
    } //PrintAllQualified
} //HoldsStrings
//end of class HoldsStrings

// This class contains a few sample methods
class StringFuncs
{
    // This method prints a string that it is passed if the string starts 
    // with a vowel
    public static void ConStart(String str)
    {
        if (!(str.get_Chars(0) == 'a' || str.get_Chars(0) == 'e'
            || str.get_Chars(0) == 'i' || str.get_Chars(0) == 'o'
            || str.get_Chars(0) == 'u')) {
            Console.WriteLine(str);
        }
    } //ConStart

    // This method prints a string that it is passed if the string starts with
    // a consonant
    public static void VowelStart(String str)
    {
        if (str.get_Chars(0) == 'a' || str.get_Chars(0) == 'e'
            || str.get_Chars(0) == 'i' || str.get_Chars(0) == 'o'
            || str.get_Chars(0) == 'u') {
            Console.WriteLine(str);
        }
    } //VowelStart
} //StringFuncs

// This class demonstrates using Delegates, including using the Remove and
// Combine methods to create and modify delegate combinations.
class Test
{
    public static void main(String[] args)
    {
        // Declare the HoldsStrings class and add some strings
        HoldsStrings myHoldsStrings = new HoldsStrings();
        myHoldsStrings.addstring("This");
        myHoldsStrings.addstring("is");
        myHoldsStrings.addstring("a");
        myHoldsStrings.addstring("multicast");
        myHoldsStrings.addstring("delegate");
        myHoldsStrings.addstring("example");
        // Create two delegates individually using different methods
        HoldsStrings.CheckAndPrintDelegate ConStartDel = 
            new HoldsStrings.CheckAndPrintDelegate(StringFuncs.ConStart);
        HoldsStrings.CheckAndPrintDelegate VowStartDel = 
            new HoldsStrings.CheckAndPrintDelegate(StringFuncs.VowelStart);
        // Demonstrate that MulticastDelegates may store only one delegate
        Delegate DelegateList[];
        // Returns an array of all delegates stored in the linked list of the
        // MulticastDelegate. In these cases the lists will hold only one 
        // (Multicast) delegate
        DelegateList = ConStartDel.GetInvocationList();
        Console.WriteLine("ConStartDel contains " + DelegateList.get_Length() 
            + " delegate(s).");
        DelegateList = VowStartDel.GetInvocationList();
        Console.WriteLine("ConStartVow contains " + DelegateList.get_Length() 
            + " delegate(s).");
        // Determine whether the delegates are System.Multicast delegates
        // if (ConStartDel is System.MulticastDelegate && VowStartDel is 
        // System.MulticastDelegate) {
        Console.WriteLine("ConStartDel and ConStartVow are " 
            + "System.MulticastDelegates");
        // }
        // Run the two single delegates one after the other
        Console.WriteLine("Running ConStartDel delegate:");
        myHoldsStrings.PrintAllQualified(ConStartDel);
        Console.WriteLine("Running VowStartDel delegate:");
        myHoldsStrings.PrintAllQualified(VowStartDel);
        // Create a new, empty MulticastDelegate
        HoldsStrings.CheckAndPrintDelegate multiDel;
        // Delegate.Combine receives an unspecified number of MulticastDelegates
        // as parameters
        multiDel = (HoldsStrings.CheckAndPrintDelegate)(Delegate.Combine(
            ConStartDel, VowStartDel));
        // How many delegates is this delegate holding?
        DelegateList = multiDel.GetInvocationList();
        Console.WriteLine("\nMulitDel contains " + DelegateList.get_Length() 
            + " delegates.");
        // What happens when this mulitcast delegate is passed to 
        // PrintAllQualified
        Console.WriteLine("Running the multiple delegate that combined the "
            + "first two");
        myHoldsStrings.PrintAllQualified(multiDel);
        // The Remove and Combine methods modify the multiple delegate
        multiDel = (HoldsStrings.CheckAndPrintDelegate)(Delegate.Remove(
            multiDel, VowStartDel));
        multiDel = (HoldsStrings.CheckAndPrintDelegate)(Delegate.Combine(
            multiDel, ConStartDel));
        // Finally, pass the combined delegates to PrintAllQualified again
        Console.WriteLine("\nRunning the multiple delegate that contains two " 
            + "copies of ConStartDel:");
        myHoldsStrings.PrintAllQualified(multiDel);
        return;
    } //main 
} //Test

Vererbungshierarchie

System.Object
   System.Delegate
    System.MulticastDelegate
       Abgeleitete Klassen

Threadsicherheit

Alle öffentlichen statischen (Shared in Visual Basic) Member dieses Typs sind threadsicher. Bei Instanzmembern ist die Threadsicherheit nicht gewährleistet.

Plattformen

Windows 98, Windows 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile für Pocket PC, Windows Mobile für Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

.NET Framework unterstützt nicht alle Versionen sämtlicher Plattformen. Eine Liste der unterstützten Versionen finden Sie unter Systemanforderungen.

Versionsinformationen

.NET Framework

Unterstützt in: 2.0, 1.1, 1.0

.NET Compact Framework

Unterstützt in: 2.0, 1.0

Siehe auch

Referenz

MulticastDelegate-Member
System-Namespace