Как асинхронно реализовывать операции службы
В приложениях Windows Communication Foundation (WCF) операция службы может быть реализована асинхронно или синхронно без жесткого задания способа вызова клиентом. Например, асинхронные операции службы могут вызываться синхронно или синхронные операции службы могут вызываться асинхронно. Пример асинхронного вызова операции из клиентского приложения см. в разделе Как асинхронно вызывать операции службы WCF. Дополнительные сведения синхронных и асинхронных режимах см. в разделах Создание контрактов служб и Синхронные и асинхронные операции. В этом разделе описывается базовая структура асинхронной операции службы, код не завершен. Полный образец стороны службы и клиента приведен в разделе Асинхронное взаимодействие.
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 разделе Asynchronous Programming Design Patterns.
Пометьте метод Begin пары асинхронных методов атрибутом System.ServiceModel.OperationContractAttribute и задайте для свойства System.ServiceModel.OperationContractAttribute.AsyncPattern значение true. Например, приведенный ниже код выполняет шаги 1 и 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); }
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".
Пример
В следующих примерах кода показаны:
Интерфейс контракта службы с:
Синхронной операцией
SampleMethod
.Асинхронной операцией
BeginSampleMethod
.Парой асинхронных операций
BeginServiceAsyncMethod
/EndServiceAsyncMethod
.
Реализацией службы с использованием объекта 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
}
}