MulticastDelegate Classe

Définition

public ref class MulticastDelegate abstract : Delegate

public abstract class MulticastDelegate : Delegate

[System.Serializable]
public abstract class MulticastDelegate : Delegate

[System.Serializable]
[System.Runtime.InteropServices.ComVisible(true)]
public abstract class MulticastDelegate : Delegate

type MulticastDelegate = class
    inherit Delegate

[<System.Serializable>]
type MulticastDelegate = class
    inherit Delegate

[<System.Serializable>]
[<System.Runtime.InteropServices.ComVisible(true)>]
type MulticastDelegate = class
    inherit Delegate

Public MustInherit Class MulticastDelegate
Inherits Delegate

Héritage

Object

Delegate

MulticastDelegate

Attributs

SerializableAttribute ComVisibleAttribute

Exemples

L’exemple suivant définit une classe, StringContainerqui inclut une collection de chaînes. L’un de ses membres est le CheckAndDisplayDelegate délégué, qui est utilisé pour afficher des chaînes stockées dans un StringContainer objet qui répondent à des critères particuliers. Le délégué prend une chaîne unique en tant que paramètre et retourne void (ou, dans Visual Basic, il s'agit d'une procédure Sub). Il inclut également une méthode, DisplayAllQualifiedqui a un paramètre unique, un CheckAndDisplayDelegate délégué. Cela permet à la méthode d’être appelée et d’afficher un ensemble de chaînes filtrées en fonction des méthodes que le délégué contient.

L’exemple définit également une classe utilitaire, StringExtensionsqui a deux méthodes :

• ConStart, qui affiche des chaînes commençant par une consonne.

• VowelStart, qui affiche des chaînes commençant par une voyelle.

Notez que les deux méthodes incluent un paramètre de chaîne unique et un retour void. En d’autres termes, les deux méthodes peuvent être affectées au CheckAndDisplayDelegate délégué.

La Test.Main méthode est le point d’entrée de l’application. Il instancie un StringContainer objet, le remplit avec des chaînes et crée deux CheckAndDisplayDelegate délégués, conStart et vowelStartappelle une méthode unique. Il appelle ensuite la Delegate.Combine méthode pour créer le multipleDelegates délégué, qui contient initialement les délégués et ConStart les VowelStart délégués. Notez que lorsque le multipleDelegates délégué est appelé, il affiche toutes les chaînes de la collection dans leur ordre d’origine. Cela est dû au fait que chaque lettre est transmise séparément à chaque délégué, et chaque lettre répond aux critères de filtrage d’un seul des deux délégués. Enfin, après les appels à Delegate.Remove et Delegate.Combineles deux multipleDelegatesconStart délégués. Lorsqu’elle est appelée, chaque chaîne de l’objet StringContainer s’affiche deux fois.

using System;
using System.Collections.Generic;

class StringContainer
{
   // Define a delegate to handle string display.
   public delegate void CheckAndDisplayDelegate(string str);

   // A generic list object that holds the strings.
   private List<String> container = new List<String>();

   // A method that adds strings to the collection.
   public void AddString(string str)
   {
      container.Add(str);
   }

   // Iterate through the strings and invoke the method(s) that the delegate points to.
   public void DisplayAllQualified(CheckAndDisplayDelegate displayDelegate)
   {
      foreach (var str in container) {
         displayDelegate(str);
      }
   }
 }

// This class defines some methods to display strings.
class StringExtensions
{
   // Display a string if it starts with a consonant.
   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);
   }

   // Display a string if it starts with a vowel.
   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);
   }
}

// Demonstrate the use of delegates, including the Remove and
// Combine methods to create and modify delegate combinations.
class Test
{
   static public void Main()
   {
      // Declare the StringContainer class and add some strings
      StringContainer container = new StringContainer();
      container.AddString("This");
      container.AddString("is");
      container.AddString("a");
      container.AddString("multicast");
      container.AddString("delegate");
      container.AddString("example");

      // Create two delegates individually using different methods.
      StringContainer.CheckAndDisplayDelegate conStart = StringExtensions.ConStart;
      StringContainer.CheckAndDisplayDelegate vowelStart = StringExtensions.VowelStart;

      // Get the list of all delegates assigned to this MulticastDelegate instance.
      Delegate[] delegateList = conStart.GetInvocationList();
      Console.WriteLine("conStart contains {0} delegate(s).", delegateList.Length);
      delegateList = vowelStart.GetInvocationList();
      Console.WriteLine("vowelStart contains {0} delegate(s).\n", delegateList.Length);

      // Determine whether the delegates are System.Multicast delegates.
      if (conStart is System.MulticastDelegate && vowelStart is System.MulticastDelegate)
          Console.WriteLine("conStart and vowelStart are derived from MulticastDelegate.\n");

      // Execute the two delegates.
      Console.WriteLine("Executing the conStart delegate:");
      container.DisplayAllQualified(conStart);
      Console.WriteLine();
      Console.WriteLine("Executing the vowelStart delegate:");
      container.DisplayAllQualified(vowelStart);
      Console.WriteLine();

      // Create a new MulticastDelegate and call Combine to add two delegates.
      StringContainer.CheckAndDisplayDelegate multipleDelegates =
            (StringContainer.CheckAndDisplayDelegate) Delegate.Combine(conStart, vowelStart);

      // How many delegates does multipleDelegates contain?
      delegateList = multipleDelegates.GetInvocationList();
      Console.WriteLine("\nmultipleDelegates contains {0} delegates.\n",
                        delegateList.Length);

      // Pass this multicast delegate to DisplayAllQualified.
      Console.WriteLine("Executing the multipleDelegate delegate.");
      container.DisplayAllQualified(multipleDelegates);

      // Call remove and combine to change the contained delegates.
      multipleDelegates = (StringContainer.CheckAndDisplayDelegate) Delegate.Remove(multipleDelegates, vowelStart);
      multipleDelegates = (StringContainer.CheckAndDisplayDelegate) Delegate.Combine(multipleDelegates, conStart);

      // Pass multipleDelegates to DisplayAllQualified again.
      Console.WriteLine("\nExecuting the multipleDelegate delegate with two conStart delegates:");
      container.DisplayAllQualified(multipleDelegates);
   }
}
// The example displays the following output:
//    conStart contains 1 delegate(s).
//    vowelStart contains 1 delegate(s).
//
//    conStart and vowelStart are derived from MulticastDelegate.
//
//    Executing the conStart delegate:
//    This
//    multicast
//    delegate
//
//    Executing the vowelStart delegate:
//    is
//    a
//    example
//
//
//    multipleDelegates contains 2 delegates.
//
//    Executing the multipleDelegate delegate.
//    This
//    is
//    a
//    multicast
//    delegate
//    example
//
//    Executing the multipleDelegate delegate with two conStart delegates:
//    This
//    This
//    multicast
//    multicast
//    delegate
//    delegate

module Test

open System

// Define a delegate to handle string display.
type CheckAndDisplayDelegate = delegate of string -> unit

type StringContainer() =
    // A generic ResizeArray object that holds the strings.
    let container = ResizeArray()

    // A method that adds strings to the collection.
    member _.AddString(str) =
        container.Add str

    // Iterate through the strings and invoke the method(s) that the delegate points to.
    member _.DisplayAllQualified(displayDelegate: CheckAndDisplayDelegate) =
        for str in container do
            displayDelegate.Invoke str

// This module defines some functions to display strings.
module StringExtensions =
    // Display a string if it starts with a consonant.
    let conStart (str: string) =
        match str[0] with
        | 'a' | 'e' | 'i' | 'o' | 'u' -> ()
        | _ -> printfn $"{str}"
 
    // Display a string if it starts with a vowel.
    let vowelStart (str: string) =
        match str[0] with
        | 'a' | 'e' | 'i' | 'o' | 'u' -> printfn $"{str}"
        | _ -> ()
 
// Demonstrate the use of delegates, including the Remove and
// Combine methods to create and modify delegate combinations.
[<EntryPoint>]
let main _ =
    // Declare the StringContainer class and add some strings
    let container = StringContainer()
    container.AddString "This"
    container.AddString "is"
    container.AddString "a"
    container.AddString "multicast"
    container.AddString "delegate"
    container.AddString "example"

    // Create two delegates individually using different methods.
    let conStart = CheckAndDisplayDelegate StringExtensions.conStart
    let vowelStart = CheckAndDisplayDelegate StringExtensions.vowelStart 

    // Get the list of all delegates assigned to this MulticastDelegate instance.
    let delegateList = conStart.GetInvocationList()
    printfn $"conStart contains {delegateList.Length} delegate(s)."
    let delegateList = vowelStart.GetInvocationList()
    printfn $"vowelStart contains {delegateList.Length} delegate(s).\n"

    // Determine whether the delegates are System.Multicast delegates.
    if box conStart :? System.MulticastDelegate && box vowelStart :? System.MulticastDelegate then
        printfn "conStart and vowelStart are derived from MulticastDelegate.\n"

    // Execute the two delegates.
    printfn "Executing the conStart delegate:"
    container.DisplayAllQualified conStart
    printfn "\nExecuting the vowelStart delegate:"
    container.DisplayAllQualified vowelStart
    printfn ""

    // Create a new MulticastDelegate and call Combine to add two delegates.
    let multipleDelegates =
        Delegate.Combine(conStart, vowelStart) :?> CheckAndDisplayDelegate

    // How many delegates does multipleDelegates contain?
    let delegateList = multipleDelegates.GetInvocationList()
    printfn $"\nmultipleDelegates contains {delegateList.Length} delegates.\n"

    // Pass this multicast delegate to DisplayAllQualified.
    printfn "Executing the multipleDelegate delegate."
    container.DisplayAllQualified multipleDelegates

    // Call remove and combine to change the contained delegates.
    let multipleDelegates = Delegate.Remove(multipleDelegates, vowelStart) :?> CheckAndDisplayDelegate
    let multipleDelegates = Delegate.Combine(multipleDelegates, conStart) :?> CheckAndDisplayDelegate

    // Pass multipleDelegates to DisplayAllQualified again.
    printfn "\nExecuting the multipleDelegate delegate with two conStart delegates:"
    printfn $"{multipleDelegates}"
    0
// The example displays the following output:
//    conStart contains 1 delegate(s).
//    vowelStart contains 1 delegate(s).
//
//    conStart and vowelStart are derived from MulticastDelegate.
//
//    Executing the conStart delegate:
//    This
//    multicast
//    delegate
//
//    Executing the vowelStart delegate:
//    is
//    a
//    example
//
//
//    multipleDelegates contains 2 delegates.
//
//    Executing the multipleDelegate delegate.
//    This
//    is
//    a
//    multicast
//    delegate
//    example
//
//    Executing the multipleDelegate delegate with two conStart delegates:
//    This
//    This
//    multicast
//    multicast
//    delegate
//    delegate

Imports System.Collections.Generic

Class StringContainer
    ' Define a delegate to handle string display. 
    Delegate Sub CheckAndPrintDelegate(ByVal str As String)

    ' A generic list object that holds the strings.
    Private container As New List(Of String)()

     ' A method that adds strings to the collection. 
     Public Sub AddString(ByVal s As String)
        container.Add(s)
    End Sub

    ' Iterate through the strings and invoke the method(s) that the delegate points to.
    Public Sub DisplayAllQualified(ByVal displayDelegate As CheckAndPrintDelegate)
        For Each s In container
            displayDelegate(s)
        Next
    End Sub
End Class

' This class defines some methods to display strings. 
Class StringExtensions
    ' Display a string if it starts with a consonant. 
    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 

    ' Display a string if it starts with a vowel.
    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 
End Class 

' Demonstrate the use of delegates, including the Remove and 
' Combine methods to create and modify delegate combinations. 
Class Test
    Public Shared Sub Main()
        ' Declare the StringContainer class and add some strings
        Dim container As New StringContainer()
        container.AddString("this")
        container.AddString("is")
        container.AddString("a")
        container.AddString("multicast")
        container.AddString("delegate")
        container.AddString("example")

        ' Create two delegates individually using different methods.
        Dim constart As StringContainer.CheckAndPrintDelegate = AddressOf StringExtensions.ConStart
        Dim vowelStart As StringContainer.CheckAndPrintDelegate = AddressOf StringExtensions.VowelStart

        ' Get the list of all delegates assigned to this MulticastDelegate instance. 
        Dim delegateList() As [Delegate] = conStart.GetInvocationList()
        Console.WriteLine("conStart contains {0} delegate(s).", delegateList.Length)
        delegateList = vowelStart.GetInvocationList()
        Console.WriteLine("vowelStart contains {0} delegate(s).", delegateList.Length)
        Console.WriteLine()
        
        ' Determine whether the delegates are System.Multicast delegates
        If TypeOf conStart Is System.MulticastDelegate And TypeOf vowelStart Is System.MulticastDelegate Then
            Console.WriteLine("conStart and vowelStart are derived from MulticastDelegate.")
            Console.WriteLine()
        End If

        ' Run the two single delegates one after the other.
        Console.WriteLine("Executing the conStart delegate:")
        container.DisplayAllQualified(conStart)
        Console.WriteLine("Executing the vowelStart delegate:")
        container.DisplayAllQualified(vowelStart)
        Console.WriteLine()

        ' Create a new MulticastDelegate and call Combine to add two delegates.
        Dim multipleDelegates As StringContainer.CheckAndPrintDelegate = 
                  CType([Delegate].Combine(conStart, vowelStart), 
                  StringContainer.CheckAndPrintDelegate)

        ' How many delegates does multipleDelegates contain?
        delegateList = multipleDelegates.GetInvocationList()
        Console.WriteLine("{1}multipleDelegates contains {0} delegates.{1}",
                          delegateList.Length, vbCrLf)

        ' Pass this mulitcast delegate to DisplayAllQualified.
        Console.WriteLine("Executing the multipleDelegate delegate.")
        container.DisplayAllQualified(multipleDelegates)

        ' Call remove and combine to change the contained delegates.
        multipleDelegates = CType([Delegate].Remove(multipleDelegates, vowelStart), 
                            StringContainer.CheckAndPrintDelegate)
        multipleDelegates = CType([Delegate].Combine(multipleDelegates, conStart), 
                            StringContainer.CheckAndPrintDelegate)

        ' Pass multipleDelegates to DisplayAllQualified again.
        Console.WriteLine()
        Console.WriteLine("Executing the multipleDelegate delegate with two conStart delegates:")
        container.DisplayAllQualified(multipleDelegates)
    End Sub 
End Class 
' The example displays the following output:
'    conStart contains 1 delegate(s).
'    vowelStart contains 1 delegate(s).
'    
'    conStart and vowelStart are derived from MulticastDelegate.
'    
'    Executing the conStart delegate:
'    This
'    multicast
'    delegate
'    
'    Executing the vowelStart delegate:
'    is
'    a
'    example
'    
'    
'    multipleDelegates contains 2 delegates.
'    
'    Executing the multipleDelegate delegate.
'    This
'    is
'    a
'    multicast
'    delegate
'    example
'    
'    Executing the multipleDelegate delegate with two conStart delegates:
'    This
'    This
'    multicast
'    multicast
'    delegate
'    delegate

Remarques

MulticastDelegate est une classe spéciale. Les compilateurs et d’autres outils peuvent dériver de cette classe, mais vous ne pouvez pas en dériver explicitement. Il en va de même pour la Delegate classe.

En plus des méthodes dont les types délégués héritent MulticastDelegate, le Common Language Runtime fournit deux méthodes spéciales : BeginInvoke et EndInvoke. Pour plus d’informations sur ces méthodes, consultez Appel asynchrone de méthodes synchrones.

A MulticastDelegate a une liste liée de délégués, appelée liste d’appel, composée d’un ou plusieurs éléments. Lorsqu’un délégué de multidiffusion est appelé, les délégués de la liste d’appel sont appelés de façon synchrone dans l’ordre dans lequel ils apparaissent. Si une erreur se produit pendant l’exécution de la liste, une exception est levée.