MulticastDelegate Classe

Definizione

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

Ereditarietà

Object

Delegate

MulticastDelegate

Attributi

SerializableAttribute ComVisibleAttribute

Esempio

Nell'esempio seguente viene definita una classe , StringContainer, che include una raccolta di stringhe. Uno dei relativi membri è il CheckAndDisplayDelegate delegato , che viene usato per visualizzare le stringhe archiviate in un StringContainer oggetto che soddisfa criteri specifici. Il delegato accetta una singola stringa come parametro e restituisce void (o, in Visual Basic, è una routine Sub). Include anche un metodo, DisplayAllQualified, che ha un singolo parametro, un CheckAndDisplayDelegate delegato. In questo modo è possibile chiamare il metodo e visualizzare un set di stringhe filtrate in base ai metodi contenuti dal delegato.

L'esempio definisce anche una classe di utilità, StringExtensions, che dispone di due metodi:

• ConStart, che visualizza le stringhe che iniziano con una consonante.

• VowelStart, che visualizza le stringhe che iniziano con una vocale.

Si noti che entrambi i metodi includono un singolo parametro stringa e restituiscono void. In altre parole, entrambi i metodi possono essere assegnati al CheckAndDisplayDelegate delegato.

Il Test.Main metodo è il punto di ingresso dell'applicazione. Crea un'istanza di un StringContainer oggetto, lo popola con stringhe e crea due CheckAndDisplayDelegate delegati e conStartvowelStart, che richiamano un singolo metodo. Chiama quindi il Delegate.Combine metodo per creare il multipleDelegates delegato, che inizialmente contiene i ConStart delegati e VowelStart . Si noti che quando viene richiamato il multipleDelegates delegato, vengono visualizzate tutte le stringhe nella raccolta nell'ordine originale. Ciò è dovuto al fatto che ogni lettera viene passata separatamente a ogni delegato e ogni lettera soddisfa i criteri di filtro di uno dei due delegati. Infine, dopo le chiamate a Delegate.Remove e Delegate.Combine, multipleDelegates contiene due conStart delegati. Quando viene richiamato, ogni stringa nell'oggetto StringContainer viene visualizzata due volte.

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

Commenti

MulticastDelegate è una classe speciale. I compilatori e altri strumenti possono derivare da questa classe, ma non è possibile derivarlo in modo esplicito. Lo stesso vale per la Delegate classe .

Oltre ai metodi che delegano i tipi ereditano da MulticastDelegate, Common Language Runtime fornisce due metodi speciali: BeginInvoke e EndInvoke. Per altre informazioni su questi metodi, vedere Chiamata asincrona di metodi sincroni.

Un MulticastDelegate oggetto ha un elenco collegato di delegati, denominato elenco chiamate, costituito da uno o più elementi. Quando viene richiamato un delegato multicast, i delegati nell'elenco chiamate vengono chiamati in modo sincrono nell'ordine in cui vengono visualizzati. Se si verifica un errore durante l'esecuzione dell'elenco, viene generata un'eccezione.