WCF服務創建與拋出強類型SOAP Fault

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前面的文章《WCF服務的異常消息》中介紹過，如果WCF Service發生異常時，Service會將異常序列化為SOAP Fault并發送給客戶端。

默認情況下，出于安全原因，WCF Service中未處理的異常的詳細信息不會包括在發送給客戶的SOAP Fault里，你只能看到一個通用的SOAP Fault（“The server was unable to PRocess the request due to an internal error.”）。在調試程序的時候，如果想在SOAP Fault中包含異常的詳細信息，可以修改服務器的配置文件。

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

SOAP Fault是xml格式，與平臺無關。通常一個SOAP Fault包含以下節點

(1) faultcode

(2) faultstring

(3) detail

Detail節點可以用來包括自定義XML信息。

WCF Service在發生異常時應拋出FaultException或FaultException<T>，而不應該拋出.NET Exception，出于以下兩個原因：

（1）未處理的.NET Exception會使服務器與客戶端之間的channel變為Fault狀態，繼而導致client proxy無法使用。

（2）.NET Exception只能被.NET平臺理解，而FaultException與平臺無關。如果想跨平臺使用，需要使用FaultException。

下面還是以中《WCF服務的異常消息》的例子來分別演示如何拋出與處理FaultException與強類型的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）使用強類型FaultException<T>

（1）創建一個自定義SOAP Fault類

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來指示哪個操作可以使用哪個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>