AsyncCallback Gedelegeerde

Definitie

public delegate void AsyncCallback(IAsyncResult ^ ar);

public delegate void AsyncCallback(IAsyncResult ar);

[System.Serializable]
public delegate void AsyncCallback(IAsyncResult ar);

[System.Serializable]
[System.Runtime.InteropServices.ComVisible(true)]
public delegate void AsyncCallback(IAsyncResult ar);

type AsyncCallback = delegate of IAsyncResult -> unit

[<System.Serializable>]
type AsyncCallback = delegate of IAsyncResult -> unit

[<System.Serializable>]
[<System.Runtime.InteropServices.ComVisible(true)>]
type AsyncCallback = delegate of IAsyncResult -> unit

Public Delegate Sub AsyncCallback(ar As IAsyncResult)

Parameters

Kenmerken

SerializableAttribute ComVisibleAttribute

Voorbeelden

In het volgende codevoorbeeld ziet u hoe u asynchrone methoden gebruikt in de klasse Dns om DNS-gegevens (Domain Name System) op te halen voor door de gebruiker opgegeven computers. In dit voorbeeld wordt een AsyncCallback-delegate gemaakt die verwijst naar de ProcessDnsInformation-methode. Deze methode wordt eenmaal aangeroepen voor elke asynchrone aanvraag voor DNS-gegevens.

/*
The following example demonstrates using asynchronous methods to
get Domain Name System information for the specified host computers.
This example uses a delegate to obtain the results of each asynchronous
operation.
*/

using System;
using System.Net;
using System.Net.Sockets;
using System.Threading;
using System.Collections.Specialized;
using System.Collections;

namespace Examples.AdvancedProgramming.AsynchronousOperations
{
    public class UseDelegateForAsyncCallback
    {
        static int requestCounter;
        static ArrayList hostData = new ArrayList();
        static StringCollection hostNames = new StringCollection();
        static void UpdateUserInterface()
        {
            // Print a message to indicate that the application
            // is still working on the remaining requests.
            Console.WriteLine("{0} requests remaining.", requestCounter);
        }
        public static void Main()
        {
            // Create the delegate that will process the results of the
            // asynchronous request.
            AsyncCallback callBack = new AsyncCallback(ProcessDnsInformation);
            string host;
            do
            {
                Console.Write(" Enter the name of a host computer or <enter> to finish: ");
                host = Console.ReadLine();
                if (host.Length > 0)
                {
                    // Increment the request counter in a thread safe manner.
                    Interlocked.Increment(ref requestCounter);
                    // Start the asynchronous request for DNS information.
                    Dns.BeginGetHostEntry(host, callBack, host);
                 }
            } while (host.Length > 0);
            // The user has entered all of the host names for lookup.
            // Now wait until the threads complete.
            while (requestCounter > 0)
            {
                UpdateUserInterface();
            }
            // Display the results.
            for (int i = 0; i< hostNames.Count; i++)
            {
                object data = hostData [i];
                string message = data as string;
                // A SocketException was thrown.
                if (message != null)
                {
                    Console.WriteLine("Request for {0} returned message: {1}",
                        hostNames[i], message);
                    continue;
                }
                // Get the results.
                IPHostEntry h = (IPHostEntry) data;
                string[] aliases = h.Aliases;
                IPAddress[] addresses = h.AddressList;
                if (aliases.Length > 0)
                {
                    Console.WriteLine("Aliases for {0}", hostNames[i]);
                    for (int j = 0; j < aliases.Length; j++)
                    {
                        Console.WriteLine("{0}", aliases[j]);
                    }
                }
                if (addresses.Length > 0)
                {
                    Console.WriteLine("Addresses for {0}", hostNames[i]);
                    for (int k = 0; k < addresses.Length; k++)
                    {
                        Console.WriteLine("{0}",addresses[k].ToString());
                    }
                }
            }
       }

        // The following method is called when each asynchronous operation completes.
        static void ProcessDnsInformation(IAsyncResult result)
        {
            string hostName = (string) result.AsyncState;
            hostNames.Add(hostName);
            try
            {
                // Get the results.
                IPHostEntry host = Dns.EndGetHostEntry(result);
                hostData.Add(host);
            }
            // Store the exception message.
            catch (SocketException e)
            {
                hostData.Add(e.Message);
            }
            finally
            {
                // Decrement the request counter in a thread-safe manner.
                Interlocked.Decrement(ref requestCounter);
            }
        }
    }
}

// The following example demonstrates using asynchronous methods to
// get Domain Name System information for the specified host computers.
// This example uses a delegate to obtain the results of each asynchronous
// operation.

open System
open System.Net
open System.Net.Sockets
open System.Threading
open System.Collections.Specialized

let mutable requestCounter = 0
let hostData = ResizeArray<Result<IPHostEntry, string>>()
let hostNames = StringCollection()

let updateUserInterface () =
    // Print a message to indicate that the application
    // is still working on the remaining requests.
    printfn $"{requestCounter} requests remaining."

// The following function is called when each asynchronous operation completes.
let processDnsInformation (result: IAsyncResult) =
    string result.AsyncState
    |> hostNames.Add 
    |> ignore
    try
        try
            // Get the results.
            Dns.EndGetHostEntry result
            |> Ok
            |> hostData.Add
        // Store the exception message.
        with :? SocketException as e ->
            Error e.Message
            |> hostData.Add 
    finally
        // Decrement the request counter in a thread-safe manner.
        Interlocked.Decrement &requestCounter 
        |> ignore

// Create the delegate that will process the results of the asynchronous request.
let callBack = AsyncCallback processDnsInformation

let mutable host = " "
while host.Length > 0 do
    printf " Enter the name of a host computer or <enter> to finish: "
    host <- stdin.ReadLine()
    if host.Length > 0 then
        // Increment the request counter in a thread safe manner.
        Interlocked.Increment &requestCounter |> ignore
        // Start the asynchronous request for DNS information.
        Dns.BeginGetHostEntry(host, callBack, host) |> ignore

// The user has entered all of the host names for lookup.
// Now wait until the threads complete.
while requestCounter > 0 do
    updateUserInterface ()

// Display the results.
for i = 0 to hostNames.Count - 1 do
    match hostData[i] with 
    | Error message ->
        // A SocketException was thrown.
        printfn $"Request for {hostNames[i]} returned message: {message}"
    | Ok entry ->    
        // Get the results.
        let aliases = entry.Aliases
        let addresses = entry.AddressList
        if aliases.Length > 0 then
            printfn $"Aliases for {hostNames[i]}"
            for alias in aliases do
                printfn $"{alias}"

        if addresses.Length > 0 then
            printfn $"Addresses for {hostNames[i]}"
            for address in addresses do
                printfn $"{address}"

'The following example demonstrates using asynchronous methods to
'get Domain Name System information for the specified host computers.
'This example uses a delegate to obtain the results of each asynchronous 
'operation.

Imports System.Net
Imports System.Net.Sockets
Imports System.Threading
Imports System.Collections.Specialized
Imports System.Collections

Namespace Examples.AdvancedProgramming.AsynchronousOperations

    Public Class UseDelegateForAsyncCallback
    
        Dim Shared requestCounter as Integer
        Dim Shared hostData as ArrayList = new ArrayList()
        Dim Shared hostNames as StringCollection = new StringCollection()
        Shared Sub UpdateUserInterface()
        
            ' Print a message to indicate that the application
            ' is still working on the remaining requests.
            Console.WriteLine("{0} requests remaining.", requestCounter)
        End Sub
        Public Shared Sub Main()
            ' Create the delegate that will process the results of the 
            ' asynchronous request.
            Dim callBack as AsyncCallback
            Dim host as string
            Dim i, j, k as Integer
            callback = AddressOf ProcessDnsInformation
            Do
                Console.Write(" Enter the name of a host computer or <enter> to finish: ")
                host = Console.ReadLine()
                If host.Length > 0
                    ' Increment the request counter in a thread safe manner.
                    Interlocked.Increment(requestCounter)
                    ' Start the asynchronous request for DNS information.
                    Dns.BeginGetHostEntry(host, callBack, host)
                End If
            Loop While (host.Length > 0)
            
            ' The user has entered all of the host names for lookup.
            ' Now wait until the threads complete.
            Do While requestCounter > 0
            
                UpdateUserInterface()
            Loop
            
            ' Display the results.
            For i = 0 To hostNames.Count -1
                Dim dataObject as Object = hostData (i)
                Dim message as String 
                
                ' Was a SocketException was thrown?
                If TypeOf dataObject is String
                    message = CType(dataObject, String)
                    Console.WriteLine("Request for {0} returned message: {1}", _ 
                        hostNames(i), message)
                Else
                    ' Get the results.
                    Dim h as IPHostEntry = CType(dataObject, IPHostEntry) 
                    Dim aliases() as String = h.Aliases
                    Dim addresses() as IPAddress = h.AddressList
                    If aliases.Length > 0
                        Console.WriteLine("Aliases for 0}", hostNames(i))
                        For j = 0 To aliases.Length -1
                            Console.WriteLine("{0}", aliases(j))
                        Next j
                    End If
                    If addresses.Length > 0
                        Console.WriteLine("Addresses for {0}", hostNames(i))
                        For k = 0 To addresses.Length -1
                            Console.WriteLine("{0}",addresses(k).ToString())
                        Next k
                    End If
                End If
            Next i
       End Sub

        ' The following method is called when each asynchronous operation completes.
        Shared Sub ProcessDnsInformation(result as IAsyncResult)
        
            Dim hostName as String = CType(result.AsyncState, String)
            hostNames.Add(hostName)
            Try 
                ' Get the results.
                Dim host as IPHostEntry = Dns.EndGetHostEntry(result)
                hostData.Add(host)
            ' Store the exception message.
            Catch e as SocketException
                hostData.Add(e.Message)
            Finally 
                ' Decrement the request counter in a thread-safe manner.
                Interlocked.Decrement(requestCounter)
            End Try
        End Sub
    End Class
End Namespace

Opmerkingen

Gebruik een AsyncCallback gemachtigde om de resultaten van een asynchrone bewerking in een afzonderlijke thread te verwerken. De AsyncCallback gemachtigde vertegenwoordigt een callback-methode die wordt aangeroepen wanneer de asynchrone bewerking is voltooid. De callback-methode gebruikt een IAsyncResult parameter, die vervolgens wordt gebruikt om de resultaten van de asynchrone bewerking te verkrijgen.

Zie Een Asynchrone gedelegeerde gebruiken om een Asynchrone bewerking te beëindigen en een AsyncCallback-gemachtigde te gebruiken en een AsyncCallback-gemachtigde en statusobject te gebruiken in Asynchroon patroon (EAP) op basis van gebeurtenissen.

Zie ook

• IAsyncResult
• Een AsyncCallback-gedelegeerde gebruiken om een asynchrone bewerking te beëindigen
• Een AsyncCallback-delegate en een state-object gebruiken
• Het asynchroon aanroepen van synchrone methoden
• Asynchroon patroon (EAP) op basis van gebeurtenissen
• Gebeurtenissen afhandelen en verhogen