Практическое руководство. Асинхронная реализация операции службы

Статья
03/02/2024

В приложениях Windows Communication Foundation (WCF) операция службы может быть реализована асинхронно или синхронно без диктовки клиенту, как его вызвать. Например, асинхронные операции службы можно вызывать синхронно, а синхронные операции службы можно вызывать асинхронно. Пример, показывающий асинхронный вызов операции в клиентском приложении, см. в статье "Практическое руководство. Асинхронное вызов операций службы". Дополнительные сведения об синхронных и асинхронных операциях см. в разделе "Проектирование контрактов службы" и "Синхронные" и "Асинхронные операции". В этом разделе описывается базовая структура асинхронной операции службы, код не завершен. Полный пример как службы, так и сторон клиента см. в статье "Асинхронный".

Асинхронная реализация операции службы

В контракте службы объявите пару асинхронных методов в соответствии с рекомендациями по асинхронной разработке для платформы .NET. Метод Begin принимает параметр, объект обратного вызова и объект состояния, а возвращает System.IAsyncResult; соответствующий метод End принимает System.IAsyncResult и возвращает возвращаемое значение. Дополнительные сведения об асинхронных вызовах см. в шаблонах проектирования асинхронного программирования.

Пометьте метод Begin пары асинхронных методов атрибутом System.ServiceModel.OperationContractAttribute и задайте для свойства OperationContractAttribute.AsyncPattern значение true. Например, приведенный ниже код выполняет шаги 1 и 2.

  [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

Реализуйте пару методов Begin/End в классе своей службы в соответствии с рекомендациями по асинхронной разработке. Например, в следующем примере кода показана реализация, в которой строка записывается в консоль как в части Begin, так и в части End асинхронной операции службы, и возвращаемое значение операции End возвращается клиенту. Полный пример кода см. в подразделе "Пример".

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

Пример

В следующих примерах кода показаны:

Интерфейс контракта службы с:
1. Синхронной операцией SampleMethod.
2. Асинхронной операцией BeginSampleMethod.
3. Пара асинхронных BeginServiceAsyncMethod/EndServiceAsyncMethod операций.
Реализацией службы с использованием объекта System.IAsyncResult.

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 synchronous 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.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 synchronous 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

Поделиться через

Практическое руководство. Асинхронная реализация операции службы

Асинхронная реализация операции службы

Пример

См. также

Дополнительные ресурсы