Vorgehensweise: Implementieren eines asynchronen Dienstvorgangs

In Windows Communication Foundation (WCF)-Anwendungen kann ein Dienstvorgang asynchron oder synchron implementiert werden, ohne dem Client vorzuschreiben, wie er ihn aufzurufen hat.So können z. B. asynchrone Dienstvorgänge synchron aufrufen, und synchrone Dienstvorgänge können asynchron aufgerufen werden.Ein Beispiel für das asynchrone Aufrufen eines Vorgangs in einer Clientanwendung finden Sie unter Vorgehensweise: Asynchrones Aufrufen von Dienstvorgängen.Weitere Informationen finden Sie unter zu synchronen und asynchronen Vorgängen finden Sie unter Entwerfen von Dienstverträgen und Synchrone und asynchrone Vorgänge.In diesem Thema wird die grundlegende Struktur eines asynchronen Dienstvorgangs beschrieben (der Code ist nicht vollständig).Ein ausführliches Beispiel für den Dienst und den Client finden Sie unter Asynchronous.

Asynchrones Implementieren eines Dienstvorgangs

  1. Deklarieren Sie im Dienstvertrag ein asynchrones Methodenpaar entsprechend den .NET-Richtlinien für den asynchronen Entwurf.Die Methode Begin nimmt einen Parameter, ein Rückrufobjekt und ein Statusobjekt und gibt eine System.IAsyncResult-Methode und eine entsprechende End-Methode aus, die ein System.IAsyncResult nimmt und den Rückgabewert ausgibt.Weitere Informationen zu asynchronen Anrufen finden Sie unter Entwurfsmuster für die asynchrone Programmierung.

  2. Markieren Sie die Methode Begin des asynchronen Methodenpaars mit dem Attribut System.ServiceModel.OperationContractAttribute, und legen Sie die Eigenschaft OperationContractAttribute.AsyncPattern auf true fest.Der folgende Code führt beispielsweise die Schritte 1 und 2 aus.

      [OperationContractAttribute(AsyncPattern=true)]
      IAsyncResult BeginServiceAsyncMethod(string msg, AsyncCallback callback, object asyncState);
    
      // Note: There is no OperationContractAttribute for the end method.
      string EndServiceAsyncMethod(IAsyncResult result);
    }
    
    <OperationContractAttribute(AsyncPattern:=True)> _
    Function BeginServiceAsyncMethod(ByVal msg As String, ByVal callback As AsyncCallback, ByVal asyncState As Object) As IAsyncResult
    
    ' Note: There is no OperationContractAttribute for the end method.
    Function EndServiceAsyncMethod(ByVal result As IAsyncResult) As String
     End Interface
    
  3. Implementieren Sie das Methodenpaar Begin/End in Ihrer Dienstklasse gemäß den asynchronen Entwurfsrichtlinien von .NET.Das folgende Codebeispiel zeigt eine Implementierung, in der eine Zeichenkette sowohl in den Teilen Begin als auch End des asynchronen Dienstvorgangs auf die Konsole geschrieben ist, und der Rückgabewert des Vorgangs End wird an den Client ausgegeben.Das vollständige Codebeispiel finden Sie im Abschnitt "Beispiel".

    public IAsyncResult BeginServiceAsyncMethod(string msg, AsyncCallback callback, object asyncState) 
    {
      Console.WriteLine("BeginServiceAsyncMethod called with: \"{0}\"", msg);
      return new CompletedAsyncResult<string>(msg);
    }
    
    public string EndServiceAsyncMethod(IAsyncResult r)
    {
      CompletedAsyncResult<string> result = r as CompletedAsyncResult<string>;
      Console.WriteLine("EndServiceAsyncMethod called with: \"{0}\"", result.Data);
      return result.Data;
    }
    
    Public Function BeginServiceAsyncMethod(ByVal msg As String, ByVal callback As AsyncCallback, ByVal asyncState As Object) As IAsyncResult Implements ISampleService.BeginServiceAsyncMethod
      Console.WriteLine("BeginServiceAsyncMethod called with: ""{0}""", msg)
      Return New CompletedAsyncResult(Of String)(msg)
    End Function
    
    Public Function EndServiceAsyncMethod(ByVal r As IAsyncResult) As String Implements ISampleService.EndServiceAsyncMethod
      Dim result As CompletedAsyncResult(Of String) = TryCast(r, CompletedAsyncResult(Of String))
      Console.WriteLine("EndServiceAsyncMethod called with: ""{0}""", result.Data)
      Return result.Data
    End Function
    

Beispiel

Das folgende Codebeispiel zeigt:

  1. Eine Dienstvertragschnittstelle mit:

    1. Einem synchronen SampleMethod-Vorgang.

    2. Einem asynchronen BeginSampleMethod-Vorgang.

    3. Einem asynchronen BeginServiceAsyncMethod\/EndServiceAsyncMethod-Vorgangspaar.

  2. Einer Dienstimplementierung mit einem System.IAsyncResult-Objekt.

using System;
using System.Collections.Generic;
using System.ServiceModel;
using System.Text;
using System.Threading;

namespace Microsoft.WCF.Documentation
{
  [ServiceContractAttribute(Namespace="http://microsoft.wcf.documentation")]
  public interface ISampleService{

    [OperationContractAttribute]
    string SampleMethod(string msg);

    [OperationContractAttribute(AsyncPattern = true)]
    IAsyncResult BeginSampleMethod(string msg, AsyncCallback callback, object asyncState);

    //Note: There is no OperationContractAttribute for the end method.
    string EndSampleMethod(IAsyncResult result);

    [OperationContractAttribute(AsyncPattern=true)]
    IAsyncResult BeginServiceAsyncMethod(string msg, AsyncCallback callback, object asyncState);

    // Note: There is no OperationContractAttribute for the end method.
    string EndServiceAsyncMethod(IAsyncResult result);
  }

  public class SampleService : ISampleService
  {
    #region ISampleService Members

    public string  SampleMethod(string msg)
    {
      Console.WriteLine("Called synchronous sample method with \"{0}\"", msg);
 	    return "The sychronous service greets you: " + msg;
    }

    // This asynchronously implemented operation is never called because 
    // there is a synchronous version of the same method.
    public IAsyncResult BeginSampleMethod(string msg, AsyncCallback callback, object asyncState)
    {
      Console.WriteLine("BeginSampleMethod called with: " + msg);
      return new CompletedAsyncResult<string>(msg);
    }

    public string EndSampleMethod(IAsyncResult r)
    {
      CompletedAsyncResult<string> result = r as CompletedAsyncResult<string>;
      Console.WriteLine("EndSampleMethod called with: " + result.Data);
      return result.Data;
    }

    public IAsyncResult BeginServiceAsyncMethod(string msg, AsyncCallback callback, object asyncState) 
    {
      Console.WriteLine("BeginServiceAsyncMethod called with: \"{0}\"", msg);
      return new CompletedAsyncResult<string>(msg);
    }

    public string EndServiceAsyncMethod(IAsyncResult r)
    {
      CompletedAsyncResult<string> result = r as CompletedAsyncResult<string>;
      Console.WriteLine("EndServiceAsyncMethod called with: \"{0}\"", result.Data);
      return result.Data;
    }
    #endregion
  }

  // Simple async result implementation.
  class CompletedAsyncResult<T> : IAsyncResult
  {
    T data;

    public CompletedAsyncResult(T data)
    { this.data = data; }

    public T Data
    { get { return data; } }

    #region IAsyncResult Members
    public object AsyncState
    { get { return (object)data; } }

    public WaitHandle AsyncWaitHandle
    { get { throw new Exception("The method or operation is not implemented."); } }

    public bool CompletedSynchronously
    { get { return true; } }

    public bool IsCompleted
    { get { return true; } }
    #endregion
  }
}

Imports System
Imports System.Collections.Generic
Imports System.ServiceModel
Imports System.Text
Imports System.Threading

Namespace Microsoft.WCF.Documentation
  <ServiceContractAttribute(Namespace:="http://microsoft.wcf.documentation")> _
  Public Interface ISampleService

	<OperationContractAttribute> _
	Function SampleMethod(ByVal msg As String) As String

	<OperationContractAttribute(AsyncPattern := True)> _
	Function BeginSampleMethod(ByVal msg As String, ByVal callback As AsyncCallback, ByVal asyncState As Object) As IAsyncResult

	'Note: There is no OperationContractAttribute for the end method.
	Function EndSampleMethod(ByVal result As IAsyncResult) As String

	<OperationContractAttribute(AsyncPattern:=True)> _
	Function BeginServiceAsyncMethod(ByVal msg As String, ByVal callback As AsyncCallback, ByVal asyncState As Object) As IAsyncResult

	' Note: There is no OperationContractAttribute for the end method.
	Function EndServiceAsyncMethod(ByVal result As IAsyncResult) As String
  End Interface

  Public Class SampleService
	  Implements ISampleService
	#Region "ISampleService Members"

	Public Function SampleMethod(ByVal msg As String) As String Implements ISampleService.SampleMethod
	  Console.WriteLine("Called synchronous sample method with ""{0}""", msg)
		 Return "The sychronous service greets you: " & msg
	End Function

	' This asynchronously implemented operation is never called because 
	' there is a synchronous version of the same method.
	Public Function BeginSampleMethod(ByVal msg As String, ByVal callback As AsyncCallback, ByVal asyncState As Object) As IAsyncResult Implements ISampleService.BeginSampleMethod
	  Console.WriteLine("BeginSampleMethod called with: " & msg)
	  Return New CompletedAsyncResult(Of String)(msg)
	End Function

	Public Function EndSampleMethod(ByVal r As IAsyncResult) As String Implements ISampleService.EndSampleMethod
	  Dim result As CompletedAsyncResult(Of String) = TryCast(r, CompletedAsyncResult(Of String))
	  Console.WriteLine("EndSampleMethod called with: " & result.Data)
	  Return result.Data
	End Function

	Public Function BeginServiceAsyncMethod(ByVal msg As String, ByVal callback As AsyncCallback, ByVal asyncState As Object) As IAsyncResult Implements ISampleService.BeginServiceAsyncMethod
	  Console.WriteLine("BeginServiceAsyncMethod called with: ""{0}""", msg)
	  Return New CompletedAsyncResult(Of String)(msg)
	End Function

	Public Function EndServiceAsyncMethod(ByVal r As IAsyncResult) As String Implements ISampleService.EndServiceAsyncMethod
	  Dim result As CompletedAsyncResult(Of String) = TryCast(r, CompletedAsyncResult(Of String))
	  Console.WriteLine("EndServiceAsyncMethod called with: ""{0}""", result.Data)
	  Return result.Data
	End Function
	#End Region
  End Class

  ' Simple async result implementation.
  Friend Class CompletedAsyncResult(Of T)
	  Implements IAsyncResult
	Private data_Renamed As T

	Public Sub New(ByVal data As T)
		Me.data_Renamed = data
	End Sub

	Public ReadOnly Property Data() As T
		Get
			Return data_Renamed
		End Get
	End Property

	#Region "IAsyncResult Members"
	Public ReadOnly Property AsyncState() As Object Implements IAsyncResult.AsyncState
		Get
			Return CObj(data_Renamed)
		End Get
	End Property

	Public ReadOnly Property AsyncWaitHandle() As WaitHandle Implements IAsyncResult.AsyncWaitHandle
		Get
			Throw New Exception("The method or operation is not implemented.")
		End Get
	End Property

	Public ReadOnly Property CompletedSynchronously() As Boolean Implements IAsyncResult.CompletedSynchronously
		Get
			Return True
		End Get
	End Property

	Public ReadOnly Property IsCompleted() As Boolean Implements IAsyncResult.IsCompleted
		Get
			Return True
		End Get
	End Property
	#End Region
  End Class
End Namespace

Siehe auch

Entwerfen von Dienstverträgen
Synchrone und asynchrone Vorgänge