Cómo: Implementar una operación de servicios asincrónica

En aplicaciones de Windows Communication Foundation (WCF), se puede implementar una operación de servicio de forma asincrónica o sincrónica sin dictar al cliente cómo llamarla. Por ejemplo, las operaciones de servicio asincrónicas pueden realizar llamadas sincrónicamente y a las operaciones de servicio sincrónicas se las puede llamar de manera asincrónica. Para obtener un ejemplo que muestre cómo llamar a una operación de manera asincrónica en una aplicación cliente, vea Cómo llamar a operaciones del servicio WCF de forma asincrónica. Para obtener más información sobre operaciones sincrónicas y asincrónicas, vea Diseño de contratos de servicios y Operaciones sincrónicas y asincrónicas. En este tema se describe la estructura básica de una operación de servicio asincrónica, el código no está completo. Para obtener un ejemplo completo tanto del lado del servicio como del cliente, vea Asincrónico.

Implementación de una operación de servicio de manera asincrónica

1. En su contrato de servicio, declare un par de métodos asincrónicos según las instrucciones de diseño asincrónico de .NET. El método Begin toma un parámetro, un objeto de devolución de llamada y un objeto de estado, y devuelve un System.IAsyncResult y un método End correspondiente que toma System.IAsyncResult y devuelven el valor devuelto. Para obtener más información sobre las llamadas asincrónicas, vea Asynchronous Programming Design Patterns.

2. Marque el método Begin del par de métodos asincrónicos con el atributo System.ServiceModel.OperationContractAttribute y establezca la propiedad System.ServiceModel.OperationContractAttribute.AsyncPattern en true. Por ejemplo, el código siguiente realiza los pasos 1 y 2.

     <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
   

     [OperationContractAttribute(AsyncPattern=true)]
     IAsyncResult BeginServiceAsyncMethod(string msg, AsyncCallback callback, object asyncState);
   
     // Note: There is no OperationContractAttribute for the end method.
     string EndServiceAsyncMethod(IAsyncResult result);
   }
   

3. Implemente el par de método Begin/End en su clase de servicio según las instrucciones de diseño asincrónicas. Por ejemplo, el siguiente ejemplo de código muestra una implementación en la que una cadena se escribe en la consola en porciones Begin y End de la operación de servicio asincrónica y el valor devuelto de la operación End se devuelve al cliente. Para obtener el ejemplo de código completo, consulte la sección Ejemplo.

Ejemplo

Los siguientes ejemplos de código muestran:

1. Una interfaz del contrato de servicio con:

   1. Una operación SampleMethod sincrónica.

   2. Una operación BeginSampleMethod asincrónica.

   3. Un par de operaciones BeginServiceAsyncMethod/EndServiceAsyncMethod asincrónicas.

2. Una implementación de servicio mediante un objeto System.IAsyncResult.

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

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
  }
}

Vea también

Conceptos

Diseño de contratos de servicios
Operaciones sincrónicas y asincrónicas