[WCF 学习笔记] 5. 异常处理

WCF 将服务异常(Exception)转换成 SOAP faults，传递到客户端后再次转换成 Exception。只不过缺省情况下，我们很难从中获取有意义的信息。

[ServiceContract]
public interface ICalculate
{
  [OperationContract]
  int Add(int a, int b);
}

public class CalculateService : ICalculate
{
  public int Add(int a, int b)
  {
    throw new Exception("错误！");
  }
}

客户端调用 Add 方法触发异常，信息如下：

System.ServiceModel.FaultException:The server was unable to process the request due to an internal error.For more information about the error, either turn onIncludeExceptionDetailInFaults (either from ServiceBehaviorAttribute orfrom the <serviceDebug> configuration behavior) on the server inorder to send the exception information back to the client, or turn ontracing as per the Microsoft .NET Framework 3.0 SDK documentation andinspect the server trace logs.

Server stack trace:
  在System.ServiceModel.Channels.ServiceChannel.ThrowIfFaultUnderstood(Messagereply, MessageFault fault, String action, MessageVersion version,FaultConverter faultConverter)
  ......

(我们可以使用 "(host asServiceHost).Description.Behaviors.Find<ServiceDebugBehavior>().IncludeExceptionDetailInFaults= true;" 来启动调试行为，这样也能看到具体的出错信息！ )

当然，WCF 会提供一个包装异常类 FaultException 来帮助我们处理这些问题。

[ServiceContract]
public interface ICalculate
{
  [OperationContract]
  int Add(int a, int b);
}

public class CalculateService : ICalculate
{
  public int Add(int a, int b)
  {
    throw new FaultException(new Exception("错误！").Message);
  }
}

这次输出的信息要友好得多。

System.ServiceModel.FaultException: 错误！

Server stack trace:
  在 System.ServiceModel.Channels.ServiceChannel.HandleReply(ProxyOperationRuntime operation, ProxyRpc& rpc)
  ......

另外，我们还可以通过 FaultContractAttribute 传递更详细的异常信息给客户端。

[DataContract]
public class FaultMessage
{
  [DataMember] public string Message;
  [DataMember] public int ErrorCode;
}

[ServiceContract]
public interface ICalculate
{
  [OperationContract]
  [FaultContract(typeof(FaultMessage))]
  int Add(int a, int b);
}

public class CalculateService : ICalculate
{
  public int Add(int a, int b)
  {
    FaultMessage fault = new FaultMessage();
    fault.Message = "错误信息！";
    fault.ErrorCode = 1234;

    throw new FaultException<FaultMessage>(fault, fault.Message);
  }
}

客户端代码

try
{
  CalculateClient client = new ConsoleApplication1.localhost.CalculateClient();
  client.Add(1, 2);
}
catch (FaultException<FaultMessage> e)
{
  Console.WriteLine("{0}; {1}", e.Detail.Message, e.Detail.ErrorCode);
}

-- 更详细的信息，请参考《WCF - FaultException》--