让 wcf 客户端等待回调

Question

我目前正在处理一个项目，我必须通过 wcf 客户端管理应用程序。我面临的问题是，在调用服务器后，我需要客户端等待回调。这是场景：

我调用显示窗口的服务，然后服务器应用程序处于空闲状态。当我单击窗口上的按钮时，它会回调客户端。在此期间，必须禁用客户端 UI - 它必须等待回调。您能告诉我如何实现这一目标吗？是不是跟并发模式或者Operation Contract属性有关系？

这是我的 ServiceContract 和 CallbackContract 代码：

[ServiceContract(CallbackContract = typeof(IWCFServiceCallback))]
public interface IWCFService
{
    [OperationContract]
    void OpenWindow();
}
public interface IWCFServiceCallback
{
    [OperationContract(IsOneWay = true)]
    void ReturnValue(object[] value);
}

Answer 1

不，您描述的功能与并发模式或操作合同无关。您可能需要使用信号量（Mutex、Monitor，等等）和从服务器到客户端的回调来设置信号量。

话说你描述的功能看起来很奇怪。

Answer 2

您可以通过实现异步服务操作并使用Async/Await 调用它来做到这一点。

在调用您的服务之前禁用您的客户端 UI，然后在回调返回后启用它。

https://msdn.microsoft.com/en-us/library/ms731177.aspx

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
  }
}

Answer 3

当并发模式为 ConcurrencyMode.Single 并且客户端调用服务时，服务将创建一个锁。当它调用 IsOneWay 为 false 的回调接口时，结果消息将被发送回服务。该服务将再次创建锁并将死锁，因为该锁仍然来自客户端调用。 使用 ConsurrencyMode。重入锁将在回调时偷偷释放并在返回时重新获取，以便您可以使用它。 IsOneWay=true 也是一种解决方案，因为没有结果消息被发送回服务回调。

因此，您应该能够在调用服务之前锁定您的 GUI，并在回调操作具有 IsOneWay = true 或服务配置了 ConcurrencyMode.Reentrant 时在回调中解锁它

Answer 4

感谢您的回答。我通过使用 Win32 ShowWindow 函数解决了这个问题。