在异步调用中不执行回调函数

Question

我正在尝试使用WCF进行简单的异步调用，但从不执行回调函数。任何人都可以告诉我代码有什么问题吗？

我使用Visual Studio 2008与.net 3.5

服务代码

[ServiceContract] 
public interface IService1 
{ 
    [OperationContract(AsyncPattern = true) ] 
    IAsyncResult BeginGetData(string value, AsyncCallback callback, object state); 

    string EndGetData(IAsyncResult result); 
} 

public class Service1 : IService1 
{ 

    #region IService1 Members 

    public IAsyncResult BeginGetData(string value, AsyncCallback callback, object state) 
    { 
     return new CompletedAsyncResult<string>(value, state); 
    } 

    public string EndGetData(IAsyncResult r) 
    { 
     CompletedAsyncResult<string> result = r as CompletedAsyncResult<string>; 
     return result.Data; 
    } 

    #endregion 
} 

客户端代码

class Program 
{ 
    static void Main(string[] args) 
    { 

     Service1Client client = new Service1Client(); 

     Console.WriteLine("Start async call"); 
     IAsyncResult result = client.BeginGetData("abc", callback, null); 
     Console.ReadLine(); 
    } 
    static void callback(IAsyncResult result) 
    { 
     string a = "in callback"; 

     Console.WriteLine(a); 
    } 
} 

Answer 1

你需要显式调用回调函数。

 IAsyncResult result = client.BeginGetData("abc", callback, null); 

     callback(result); 

     Console.ReadLine(); 

请参阅此处参考。

http://blogs.msdn.com/mjm/archive/2005/05/04/414793.aspx