WCF服务创建与抛出强类型SOAP Fault

原创地址：http://www.cnblogs.com/jfzhu/p/4060666.html                 

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前面的文章《WCF服务的异常消息》中介绍过，如果WCF Service发生异常时，Service会将异常序列化为SOAP Fault并发送给客户端。

默认情况下，出于安全原因，WCF Service中未处理的异常的详细信息不会包括在发送给客户的SOAP Fault里，你只能看到一个通用的SOAP Fault（“The server was unable to process the request due to an internal error.”）。在调试程序的时候，如果想在SOAP Fault中包含异常的详细信息，可以修改服务器的配置文件。

<behaviors>
  <serviceBehaviors>
    <behavior name="includeExceptionDetails">
      <serviceDebug includeExceptionDetailInFaults="true" />
    </behavior>
  </serviceBehaviors>
</behaviors>

 

SOAP Fault是XML格式，与平台无关。通常一个SOAP Fault包含以下节点

(1) faultcode

(2) faultstring

(3) detail

Detail节点可以用来包括自定义XML信息。

WCF Service在发生异常时应抛出FaultException或FaultException<T>，而不应该抛出.NET Exception，出于以下两个原因：

（1）未处理的.NET Exception会使服务器与客户端之间的channel变为Fault状态，继而导致client proxy无法使用。

（2）.NET Exception只能被.NET平台理解，而FaultException与平台无关。如果想跨平台使用，需要使用FaultException。

下面还是以中《WCF服务的异常消息》的例子来分别演示如何抛出与处理FaultException与强类型的FaultException<T>。

（一）使用FaultException

IDemoService.cs：

using System.ServiceModel;

namespace WCFDemo 
{    
    [ServiceContract(Name = "IDemoService")] 
    public interface IDemoService 
    { 
        [OperationContract]        
        int Divide(int numerator, int denominator); 
    } 
}

DemoService.cs：

using System; 
using System.ServiceModel; 
using System.ServiceModel.Activation;

namespace WCFDemo 
{ 
    [AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)] 
    public class DemoService : IDemoService 
    { 
        public int Divide(int numerator, int denominator) 
        { 
            if (denominator == 0) 
            { 
                throw new FaultException("Denominator cannot be ZERO!", new FaultCode("DivideByZeroFault")); 
            } 
            return numerator / denominator;           
        } 
    } 
}

client:

private void buttonCalculate_Click(object sender, EventArgs e) 
{ 
    try 
    {                
        textBoxResult.Text = demoServiceClient.Divide(Convert.ToInt32(textBoxNumerator.Text), Convert.ToInt32(textBoxDenominator.Text)).ToString(); 
    } 
    catch (FaultException fault) 
    { 
        MessageBox.Show(fault.Code + " - " + fault.Message); 
    } 
}

SOAP Fault XML

<s:Envelope xmlns:s="http://schemas.xmlsoap.org/soap/envelope/"> 
  <s:Body> 
    <s:Fault> 
      <faultcode>s:DivideByZeroFault</faultcode> 
      <faultstring xml:lang="en-US">Denominator cannot be ZERO!</faultstring> 
    </s:Fault> 
  </s:Body> 
</s:Envelope>

（二）使用强类型FaultException<T>

（1）创建一个自定义SOAP Fault类

DivideByZeroFault.cs：

using System.Runtime.Serialization;

namespace WCFDemo 
{ 
    [DataContract] 
    public class DivideByZeroFault 
    { 
        [DataMember] 
        public string Error { get; set; }

        [DataMember] 
        public string Detail { get; set; } 
    } 
}

（2） 在Service方法上使用FaultContractAttribute来指示哪个操作可以使用哪个Fault

IDemoService.cs：

using System.ServiceModel;

namespace WCFDemo 
{    
    [ServiceContract(Name = "IDemoService")] 
    public interface IDemoService 
    { 
        [FaultContract(typeof(DivideByZeroFault))] 
        [OperationContract]        
        int Divide(int numerator, int denominator); 
    } 
}

DemoService.cs：

using System; 
using System.ServiceModel; 
using System.ServiceModel.Activation;

namespace WCFDemo 
{ 
    [AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)] 
    public class DemoService : IDemoService 
    { 
        public int Divide(int numerator, int denominator) 
        { 
            try 
            { 
                return numerator / denominator; 
            } 
            catch (DivideByZeroException ex) 
            { 
                DivideByZeroFault fault = new DivideByZeroFault(); 
                fault.Error = ex.Message; 
                fault.Detail = "Denominator cannot be ZERO!"; 
                throw new FaultException<DivideByZeroFault>(fault); 
            } 
        } 
    } 
}

client:

private void buttonCalculate_Click(object sender, EventArgs e) 
{ 
    try 
    {                
        textBoxResult.Text = demoServiceClient.Divide(Convert.ToInt32(textBoxNumerator.Text), Convert.ToInt32(textBoxDenominator.Text)).ToString(); 
    } 
    catch (FaultException<DemoServiceReference.DivideByZeroFault> fault) 
    { 
        MessageBox.Show(fault.Detail.Error + " - " + fault.Detail.Detail); 
    } 
}

返回的SOAP Fault XML:

<s:Envelope xmlns:s="http://schemas.xmlsoap.org/soap/envelope/"> 
  <s:Body> 
    <s:Fault> 
      <faultcode>s:Client</faultcode> 
      <faultstring xml:lang="en-US">The creator of this fault did not specify a Reason.</faultstring> 
      <detail> 
        <DivideByZeroFault xmlns="http://schemas.datacontract.org/2004/07/WCFDemo" xmlns:i="http://www.w3.org/2001/XMLSchema-instance"> 
          <Detail>Denominator cannot be ZERO!</Detail> 
          <Error>Attempted to divide by zero.</Error> 
        </DivideByZeroFault> 
      </detail> 
    </s:Fault> 
  </s:Body> 
</s:Envelope>