WCF开发之异常与错误处理

对于WCF中的异常与错误处理我们必须先了解一个概念SOAP Faults，它实际上就是在服务端和客户端之间来传递错误信息的一种载体。

• 公共语言运行时（CLR）异常无法跨越服务边界
– 未捕捉异常最多到达服务通道（service channel）
– 在报告给客户端之前必须要进行序列化
• 所有的异常都被序列化为SOAP faults
– 基于标准的，可互操作的
– 给予SOAP 1.1 或者 SOAP 1.2 格式

SOAP1.1

1.1代码

< s:Envelope
xmlns:s ="http://schemas.xmlsoap.org/soap/envelope/" >
   < s:Body >
     < s:Fault >
       < faultcode  xmlns ="" > s:Client </ faultcode >
       < faultstring  xml:lang ="en-US"  xmlns ="" >
        An invalid operation has occurred.
       </ faultstring >
     </ s:Fault >
   </ s:Body >
</ s:Envelope >

SOAP1.2

代码

< s:Envelope  xmlns:s ="http://www.w3.org/2003/05/soap-envelope"
xmlns:a ="http://www.w3.org/2005/08/addressing" >
   < s:Header >
     < a:Action  s:mustUnderstand ="1" >
      http://www.w3.org/2005/08/addressing/soap/fault
     </ a:Action >
     < a:RelatesTo >
      urn:uuid:64c5619c-99c3-4a83-9bdcfcbb6f399f93 </
a:RelatesTo >
     </ s:Header >
   < s:Body >
     < s:Fault >
       < s:Code >
         < s:Value > s:Sender </ s:Value >
       </ s:Code >
       < s:Reason >
         < s:Text  xml:lang ="en-US" >
          An invalid operation
          has occurred.
         </ s:Text >
       </ s:Reason >
     </ s:Fault >
   </ s:Body >
</ s:Envelope >

非捕捉的异常
• CLR异常会从业务逻辑组件传递到服务层
• 在缺省状态下，异常的细节不会与客户端应用程序共享
• 返回一个通用的SOAP Fault

抛出异常
• 考虑下面这个CLR异常：
throw new InvalidOperationException("The method or operation is not implemented.");
• 如果没有被捕捉到，服务模型将会返回一个SOAP Fault
– 缺省情况下，异常中不包含细节信息
– 能够选择添加细节信息
• SOAP 格式依赖于绑定（binding）

IncludeExceptionDetailsInFaults（打开开关[true]就可以看到具体的异常信息了）
• IncludeExceptionDetailsInFaults
– Debugging行为控制如何对待未捕捉的异常
– 如果被打开，生成的SOAP fault中，异常细节部分将包括栈跟踪的信息
• 发送调用栈跟踪细节是有风险的
• 只用于调试目的

在<serviceDebug>区域中配置服务的行为：

代码

< system.serviceModel >
   < services >
     < service  name ="ExceptionService.Service"
    behaviorConfiguration ="serviceBehavior" >
       < endpoint  address ="http://localhost:8000/Service"
      contract ="ExceptionService.IService"  binding ="wsHttpBinding"   />
     </ service >
   </ services >
   < behaviors >
     < serviceBehaviors >
       < behavior  name ="serviceBehavior"   >
         < serviceDebug  includeExceptionDetailInFaults  ="true" />
       </ behavior >
     </ serviceBehaviors >
   </ behaviors >
</ system.serviceModel >

 

使用ServiceBehaviorAttribute来初始化行为：（code方式）
[ServiceBehaviorAttribute(IncludeExceptionDetailsInFaults=true)]
public class Service : IService

下面看一个Demo：

先提出一个知识点：

[OperationContract(IsOneWay=true)]的含义。

IsOneWay=false是默认的设置，是一种阻塞方式的调用，可以理解为同步调用，当客户端发送调用服务的请求后，客户端被阻塞，直到收到服务端处理的返回结果才继续工作，我们绝大多数的程序都是这种方式。

IsOneWay=true和异步调用方式类似，但是不完全相同。还是有区别的：纯异步的调用方式，当客户端发出调用请求后，客户端不会被阻塞，而是可以继续工作，此时客户端不会理会请求的何时被处理了，或者说是不是会被WCF处理。OneWay的话是这样的，只有当WCF通知了客户端准备开始处理请求了此时客户端才可以继续工作，不被阻塞；但是如果客户端提交的请求一直不被WCF处理，处于挂起状态的话，此时客户端会处于阻塞状态。

 

IMyServiceA代码

using  System;
using  System.Collections.Generic;
using  System.Linq;
using  System.Runtime.Serialization;
using  System.ServiceModel;
using  System.Text;

namespace  BusinessServices
{
     //  NOTE: If you change the interface name "IService1" here, you must also update the reference to "IService1" in App.config.
    [ServiceContract]
     public   interface  IMyServiceA
    {
        [OperationContract]
         void  ThrowException();
        [OperationContract(IsOneWay = true )]
         void  ThrowExceptionOneWay();
    }
}

 

 

MyService代码

using  System;
using  System.Collections.Generic;
using  System.Linq;
using  System.Runtime.Serialization;
using  System.ServiceModel;
using  System.Text;

namespace  BusinessServices
{
     //  NOTE: If you change the class name "Service1" here, you must also update the reference to "Service1" in App.config.
     public   class  MyService : IMyServiceA
    {
         public   void  ThrowException()
        {
             throw   new  Exception( " This Exception is thrown by Charles " );
        }

         public   void  ThrowExceptionOneWay()
        {
             throw   new  Exception( " This Exception is thrown by Charles " );
        }
    }
}

 

Config代码

<? xml version="1.0" encoding="utf-8"  ?>
< configuration >
   < system.web >
     < compilation  debug ="true"   />
   </ system.web >
   <!--  When deploying the service library project, the content of the config file must be added to the host's 
  app.config file. System.Configuration does not support config files for libraries.  -->
   < system.serviceModel >
     < services >
       < service  behaviorConfiguration ="BusinessServices.Service1Behavior"
        name ="BusinessServices.MyService" >
         < endpoint  address =""  binding ="wsHttpBinding"  contract ="BusinessServices.IMyServiceA" >
           < identity >
             < dns  value ="localhost"   />
           </ identity >
         </ endpoint >
         < endpoint  address ="mex"  binding ="mexHttpBinding"  contract ="IMetadataExchange"   />
         < host >
           < baseAddresses >
             < add  baseAddress ="http://localhost:8731/WCF/Charlesliu"   />
           </ baseAddresses >
         </ host >
       </ service >
     </ services >
     < behaviors >
       < serviceBehaviors >
         < behavior  name ="BusinessServices.Service1Behavior" >
           <!--  To avoid disclosing metadata information, 
          set the value below to false and remove the metadata endpoint above before deployment  -->
           < serviceMetadata  httpGetEnabled ="True" />
           <!--  To receive exception details in faults for debugging purposes, 
          set the value below to true.  Set to false before deployment 
          to avoid disclosing exception information  -->
           < serviceDebug  includeExceptionDetailInFaults ="true"   />
         </ behavior >
       </ serviceBehaviors >
     </ behaviors >
   </ system.serviceModel >
</ configuration >

 

 

ClientTest代码

using  System;
using  System.Collections.Generic;
using  System.Linq;
using  System.Text;
using  System.ServiceModel;

namespace  ClientTest
{
     class  Program
    {
         static   void  Main( string [] args)
        {
            MyServiceReference.MyServiceAClient proxy  =   new  MyServiceReference.MyServiceAClient();

             try
            {
                Console.ForegroundColor  =  ConsoleColor.Yellow;
                Console.WriteLine( " Calling proxy.ThrowException() " );
                Console.WriteLine( "" );
                Console.ResetColor();

                proxy.ThrowException();

            }
             catch  (Exception ex)
            {

                Console.WriteLine(ex.GetType().ToString());
                Console.WriteLine( " ERROR: {0} " , ex.Message);
            }

            Console.WriteLine();
            Console.WriteLine( " Proxy state after exception: {0} " , proxy.State);
            Console.WriteLine();

             if  (proxy.State  ==  CommunicationState.Faulted)
                proxy  =   new  MyServiceReference.MyServiceAClient();

             try
            {
                Console.ForegroundColor  =  ConsoleColor.Yellow;
                Console.WriteLine( " Calling proxy.ThrowExceptionOneWay() " );
                Console.ResetColor();

                proxy.ThrowExceptionOneWay();

            }
             catch  (Exception ex)
            {

                Console.WriteLine(ex.GetType().ToString());
                Console.WriteLine( " ERROR:  {0} " , ex.Message);
            }


            Console.WriteLine();
            Console.WriteLine( " Proxy state after exception: {0} " , proxy.State);
            Console.WriteLine();


             try
            {
                proxy.Close();

            }
             catch  (Exception ex)
            {

                Console.WriteLine(ex.GetType().ToString());
                Console.WriteLine( " ERROR:  {0} " , ex.Message);
            }

            Console.WriteLine();
            Console.ForegroundColor  =  ConsoleColor.Blue;
            Console.WriteLine( " Press <ENTER> to terminate Client. " );
            Console.ReadLine();
        }
    }
}

运行后：

可以看到当<serviceDebug includeExceptionDetailInFaults="true" />时，客户端可以看到具体的Exception信息了，否则只能看到一个通用的信息。对于OnWay的调用Exception是没有显示出来的，因为在Exception还没有传到客户端之前，客户端代码继续往下运行了，这就是OneWay在try-catch中特点的体现。我们还可以发现当WCF服务有异常发生时，proxy实例的state会发生变化，所以在编程中要考虑怎样处理。

 

抛出Fault（Fault指的是SOAP的fault，这和.net的Exception是两个不同的概念）：他的意思是把Fault作为数据对象发送到客户端，他的主要作用就是对异常做个包装。

• 未捕获异常表明服务模型发生了一个潜在的致命错误
• 类型：
– FaultException
– FaultException<T>
– MessageFault

FaultException
• 用于抛出简单的错误
• 可以提供错误原因与代码
• 能够提供额外的SOAP错误元素

代码

throw   new  FaultException( " An invalid operation has occurred. " );
throw   new  FaultException( new  FaultReason( " An invalid operation has occurred. " ));
throw   new  FaultException( new  FaultReason( " An invalid operation has occurred. " ), FaultCode.CreateSenderFaultCode( null ));

FaultException<T>
• 为SOAP fault提供一个强类型的<T>的简单方法
– T 必须是数据契约或者可序列化类型
• 也能够使用CLR异常类型
– 不利于互操作

throw   new  FaultException < InvalidOperationException > ( new  InvalidOperationException( " An invalid operation has occured. " ),  " Invalid operation. " ,FaultCode.CreateSenderFaultCode( null ));

 

• 为服务错误创建数据契约
–更好地用于互操作

代码

[ServiceContract(Name  =   " PhotoUploadContract " , Namespace  =
" http://www.thatindigogirl.com/samples/2006/06 " )]
public   interface  IPhotoUpload
{
    [OperationContract]
    [FaultContract( typeof (ReceiverFault))]
    [FaultContract( typeof (SenderFault))]
     void  UploadPhoto(PhotoLink fileInfo,  byte [] fileData);
}

代码

[DataContract(Namespace  =
" http://schemas.thatindigogirl.com/samples/2006/06 " )]
public   class  ReceiverFault
{
     private   string  m_message;
     private   string  m_description;
    [DataMember(Name  =   " Message " , IsRequired  =   true , Order  =   0 )]
     public   string  Message
    {
         get  {  return  m_message; }
         set  { m_message  =  value; }
    }
    [DataMember(Name  =   " Description " , IsRequired  =   false , Order  =   1 )]
     public   string  Description
    {
         get  {  return  m_description; }
         set  { m_description  =  value; }
    }
}

[DataContract(Namespace  =   " http://schemas.thatindigogirl.com/samples/2006/06 " )]
public   class  SenderFault
{
     private   string  m_message;
     private   string  m_description;
     private  List < string >  m_failedBodyElements  =   new  List < string > ();
    [DataMember(Name  =   " Message " , IsRequired  =   true , Order  =   0 )]
     public   string  Message
    {
         get  {  return  m_message; }
         set  { m_message  =  value; }
    }
    [DataMember(Name  =   " Description " , IsRequired  =   false , Order  =   1 )]
     public   string  Description
    {
         get  {  return  m_description; }
         set  { m_description  =  value; }
    }
    [DataMember(Name  =   " FailedBodyElements " , IsRequired  =   true , Order  =   2 )]
     public  List < string >  FailedBodyElements
    {
         get  {  return  m_failedBodyElements; }
         set  { m_failedBodyElements  =  value; }
    }
}

MessageFault
• SOAP Fault的CLR表示
–为了更好地控制错误元素

代码

MessageFault mfault  =  MessageFault.CreateFault(
FaultCode.CreateSenderFaultCode( null ),
new  FaultReason( " Invalid operation " ),
new  InvalidOperationException( " An invalid operation has
occurred. " ), null,  "" ,  "" );
FaultException fe  =  FaultException.CreateFault(mfault,
typeof (InvalidOperationException));
throw  fe;

 

看一个Demo：

 

代码

using  System;
using  System.Collections.Generic;
using  System.Linq;
using  System.Runtime.Serialization;
using  System.ServiceModel;
using  System.Text;

namespace  BusinessServices
{
    [ServiceContract]
     public   interface  IFaultExceptionService
    {
        [OperationContract]
        [FaultContract( typeof (InvalidOperationException))]
         void  ThrowSimpleFault();

        [OperationContract]
        [FaultContract( typeof (InvalidOperationException))]
         void  ThrowMessageFault();

        [OperationContract()]
        [FaultContract( typeof (InvalidOperationException))]
         void  ThrowFaultException();

    }
}

 

 

代码

using  System;
using  System.Collections.Generic;
using  System.Linq;
using  System.Runtime.Serialization;
using  System.ServiceModel;
using  System.Text;
using  System.ServiceModel.Channels;

namespace  BusinessServices
{
     public   class  FaultExceptionService : IFaultExceptionService
    {
         #region  IService Members

         public   void  ThrowSimpleFault()
        {

             throw   new  FaultException( " An invalid operation has occurred. " );
        }

         public   void  ThrowMessageFault()
        {
            InvalidOperationException error  =   new  InvalidOperationException( " An invalid operation has occurred. " );
            MessageFault mfault  =  MessageFault.CreateFault( new  FaultCode( " Server " ,  new  FaultCode(String.Format( " Server.{0} " , error.GetType().Name))),  new  FaultReason(error.Message), error);
            FaultException fe  =  FaultException.CreateFault(mfault,  typeof (InvalidOperationException));

             throw  fe;
        }

         public   void  ThrowFaultException()
        {
            FaultException < InvalidOperationException >  fe  =   new  FaultException < InvalidOperationException > ( new  InvalidOperationException( " An invalid operation has occured. " ),  " Invalid operation. " ,  new  FaultCode( " Server " ,  new  FaultCode(String.Format( " Server.{0} " ,  typeof (NotImplementedException)))));
             throw  fe;
        }

         #endregion
    }
}

 

代码

<? xml version="1.0" encoding="utf-8"  ?>
< configuration >
   < system.web >
     < compilation  debug ="true"   />
   </ system.web >
   <!--  When deploying the service library project, the content of the config file must be added to the host's 
  app.config file. System.Configuration does not support config files for libraries.  -->
   < system.serviceModel >
     < services >
       < service  behaviorConfiguration ="BusinessServices.Service1Behavior"
        name ="BusinessServices.FaultExceptionService" >
         < endpoint  address =""  binding ="wsHttpBinding"  contract ="BusinessServices.IFaultExceptionService" >
           < identity >
             < dns  value ="localhost"   />
           </ identity >
         </ endpoint >
         < endpoint  address ="mex"  binding ="mexHttpBinding"  contract ="IMetadataExchange"   />
         < host >
           < baseAddresses >
             < add  baseAddress ="http://localhost:8731/WCF/Charlesliu"   />
           </ baseAddresses >
         </ host >
       </ service >
     </ services >
     < behaviors >
       < serviceBehaviors >
         < behavior  name ="BusinessServices.Service1Behavior" >
           <!--  To avoid disclosing metadata information, 
          set the value below to false and remove the metadata endpoint above before deployment  -->
           < serviceMetadata  httpGetEnabled ="True" />
           <!--  To receive exception details in faults for debugging purposes, 
          set the value below to true.  Set to false before deployment 
          to avoid disclosing exception information  -->
           < serviceDebug  includeExceptionDetailInFaults ="false"   />
         </ behavior >
       </ serviceBehaviors >
     </ behaviors >
   </ system.serviceModel >
</ configuration >

 注意：includeExceptionDetailInFaults="false"

Client代码：

代码

using  System;
using  System.Collections.Generic;
using  System.Linq;
using  System.Text;
using  System.ServiceModel;

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

            MyServiceReference.FaultExceptionServiceClient proxy  =   new  ClientTest.MyServiceReference.FaultExceptionServiceClient();

             try
            {
                Console.ForegroundColor  =  ConsoleColor.Yellow;
                Console.WriteLine( " Calling proxy.ThrowSimpleFault() " );
                Console.WriteLine( "" );
                Console.ResetColor();

                proxy.ThrowSimpleFault();

            }
             catch  (FaultException fe)
            {

                Console.WriteLine(fe.GetType().ToString());
                Console.WriteLine( " ERROR: {0} " , fe.Message);

            }
             catch  (Exception ex)
            {

                Console.WriteLine(ex.GetType().ToString());
                Console.WriteLine( " ERROR: {0} " , ex.Message);
            }

            Console.WriteLine();

             try
            {
                Console.ForegroundColor  =  ConsoleColor.Yellow;
                Console.WriteLine( " Calling proxy.ThrowMessageFault() " );
                Console.ResetColor();

                proxy.ThrowMessageFault();

            }
             catch  (FaultException fe)
            {

                Console.WriteLine(fe.GetType().ToString());
                Console.WriteLine( " ERROR: {0} " , fe.Message);

            }
             catch  (Exception ex)
            {

                Console.WriteLine(ex.GetType().ToString());
                Console.WriteLine( " ERROR:  {0} " , ex.Message);
            }

            Console.WriteLine();

             try
            {
                Console.ForegroundColor  =  ConsoleColor.Yellow;
                Console.WriteLine( " Calling proxy.ThrowFaultException() " );
                Console.ResetColor();

                proxy.ThrowFaultException();
            }
             catch  (FaultException fe)
            {

                Console.WriteLine(fe.GetType().ToString());
                Console.WriteLine( " ERROR: {0} " , fe.Message);

            }
             catch  (Exception ex)
            {

                Console.WriteLine(ex.GetType().ToString());
                Console.WriteLine( " ERROR:  {0} " , ex.Message);
            }
            proxy.Close();
            Console.WriteLine();
            Console.ForegroundColor  =  ConsoleColor.Blue;
            Console.WriteLine( " Press <ENTER> to terminate Client. " );
            Console.ReadLine();
        }
    }
}

运行结果：

Fault声明 （其实上面的例子已经给出了声明的方法）
• 缺省情况下，客户端不会意识到可能抛出的错误操作
• Fault可以作为WSDL的一部分进行声明
–描述<T> 元素
– 生成包含可适用类型信息的代理
• 提供带有强类型异常的客户端（这个好处是可以根据特定的异常，进行相应的处理，比如：内存异常，IO异常，网络异常，进行相应的逻辑处理）

FaultContractAttribute
• 应用于服务契约或者操作
• 为Fault细节提供数据契约或者可序列化类型
• 操作应该抛出声明的Fault

Fault声明的方法
• 使用CLR异常提供细节信息
• 定义一些带有特性规范的核心数据契约
– ReceiverFault
– SenderFault
• 为Fault的每个特定类型定义数据契约
– FileUploadFault
– CustomerDataFault

也就是说上例中的服务端定义的具体Fault和客户端对应起来是一种好的方法，如服务端声明的是InvalidOperationException的Fault，客户款的catch改为： catch (FaultException<InvalidOperationException> fe)。

 

实现错误处理逻辑

• WCF支持集中化错误处理
–报告未捕捉的异常
– 将适当的异常转换为Fault
–修改Fault保证一致性
• 为IErrorHandler提供实现
• 添加到配置好的服务行为（service behaviors）中

 

• IErrorHandler 方法：作用就是实现了把CLR异常到Fault的包装
– ProvideFault() (这个方法的执行是在WCFServer端发生异常和WCFserver把异常传递给客户端这两个阶段之间。)
• 在发生异常后，异常消息返回并且终止会话前被调用
• 用于修改和包装返回的异常消息
• 客户端处于阻塞状态
– 不要在其内部做长时间的处理，以免客户端超时
– HandleError() (这个方法当异常返回给客户端后，在服务端被触发)
• 在异常返回给客户端之后被触发
• 不会阻塞通讯
• 通常用于记录异常，在服务端进行错误提示等操作

具体的看一个Demo：

 

IMyService 代码

using  System;
using  System.Collections.Generic;
using  System.Linq;
using  System.Runtime.Serialization;
using  System.ServiceModel;
using  System.Text;

namespace  WcfServiceLibrary1
{
     //  NOTE: If you change the interface name "IService1" here, you must also update the reference to "IService1" in App.config.
    [ServiceContract]
     public   interface  IMyService
    {
        [OperationContract]
        [FaultContract( typeof (ReceiverFaultDetail))]
        [FaultContract( typeof (SenderFaultDetail))]
         void  GetData( int  flag);
    }
}

 

 

MyService 代码

using  System;
using  System.Collections.Generic;
using  System.Linq;
using  System.Runtime.Serialization;
using  System.ServiceModel;
using  System.Text;
using  System.ServiceModel.Description;
using  System.Collections.ObjectModel;
using  System.ServiceModel.Channels;
using  System.ServiceModel.Dispatcher;

namespace  WcfServiceLibrary1
{
     //  NOTE: If you change the class name "Service1" here, you must also update the reference to "Service1" in App.config.
     public   class  MyService : IMyService
    {
         public   void  GetData( int  flag)
        {
             if  (flag  ==   0 )
            {
                 throw   new  InvalidOperationException( " error - InvalidOperationException " );
            }
        }
    }
}

 

 

Fault.cs 代码

using  System;
using  System.Collections.Generic;
using  System.Linq;
using  System.Text;
using  System.Runtime.Serialization;

namespace  WcfServiceLibrary1
{
    [DataContract]
     public   class  ReceiverFaultDetail
    {

         private   string  m_message;
         private   string  m_description;
         private   bool  m_contactAdministrator;

         public  ReceiverFaultDetail( string  message,  bool  contactAdmin)
            :  this (message,  "" , contactAdmin)
        {
        }

         public  ReceiverFaultDetail( string  message,  string  description,  bool  contactAdmin)
        {
             this .m_message  =  message;
             this .m_description  =  description;
             this .m_contactAdministrator  =  contactAdmin;
        }

        [DataMember(Name  =   " Message " , IsRequired  =   true , Order  =   0 )]
         public   string  Message
        {
             get  {  return  m_message; }
             set  { m_message  =  value; }
        }

        [DataMember(Name  =   " Description " , IsRequired  =   false , Order  =   1 )]
         public   string  Description
        {
             get  {  return  m_description; }
             set  { m_description  =  value; }
        }

        [DataMember(Name  =   " ContactAdministrator " , IsRequired  =   true , Order  =   2 )]
         public   bool  ContactAdministrator
        {
             get  {  return  m_contactAdministrator; }
             set  { m_contactAdministrator  =  value; }
        }
    }

    [DataContract]
     public   class  SenderFaultDetail
    {

         private   string  m_message;
         private   string  m_description;
         private  List < string >  m_failedBodyElements  =   new  List < string > ();


         public  SenderFaultDetail( string  message, List < string >  bodyElements)
            :  this (message,  "" , bodyElements)
        {
        }

         public  SenderFaultDetail( string  message)
            :  this (message,  "" ,  null )
        {
        }

         public  SenderFaultDetail( string  message,  string  description, List < string >  bodyElements)
        {
             this .m_message  =  message;
             this .m_description  =  description;

             if  (bodyElements  !=   null )
                 this .m_failedBodyElements  =  bodyElements;
        }

        [DataMember(Name  =   " Message " , IsRequired  =   true , Order  =   0 )]
         public   string  Message
        {
             get  {  return  m_message; }
             set  { m_message  =  value; }
        }

        [DataMember(Name  =   " Description " , IsRequired  =   false , Order  =   1 )]
         public   string  Description
        {
             get  {  return  m_description; }
             set  { m_description  =  value; }
        }

        [DataMember(Name  =   " FailedBodyElements " , IsRequired  =   true , Order  =   2 )]
         public  List < string >  FailedBodyElements
        {
             get  {  return  m_failedBodyElements; }
             set  { m_failedBodyElements  =  value; }
        }
    }
}

 

 

ServiceErrorHandler 代码

using  System;
using  System.Collections.Generic;
using  System.Linq;
using  System.Text;
using  System.ServiceModel;
using  System.ServiceModel.Dispatcher;
using  System.ServiceModel.Channels;
using  System.ServiceModel.Description;
using  System.ServiceModel.Configuration;
using  System.Collections.ObjectModel;

namespace  WcfServiceLibrary1
{
     public   class  ServiceErrorHandlerBehaviorExtensionElement : BehaviorExtensionElement
    {
         public   override  Type BehaviorType
        {
             get  {  return   typeof (ServiceErrorHandler); }
        }

         protected   override   object  CreateBehavior()
        {
             return   new  ServiceErrorHandler();
        }
    }

     public   class  ServiceErrorHandler : ServiceErrorHandlerBehaviorExtensionElement, IErrorHandler, IServiceBehavior
    {
         public   bool  HandleError(Exception error)
        {
            Console.WriteLine( " HandleError " );
             return   true ;
        }

         public   void  ProvideFault(Exception error, MessageVersion version,  ref  Message fault)
        {
             if  (fault  ==   null )
            {
                 if  (error  is  InvalidOperationException)
                {
                    FaultException < ReceiverFaultDetail >  fe  =   new  FaultException < ReceiverFaultDetail > ( new  ReceiverFaultDetail(error.Message,  true ), error.Message, FaultCode.CreateReceiverFaultCode( new  FaultCode( " InvalidOperationException " )));
                    MessageFault mf  =  fe.CreateMessageFault();

                    fault  =  Message.CreateMessage(version, mf, fe.Action);
                }
            }
        }

         public   void  AddBindingParameters(ServiceDescription serviceDescription, ServiceHostBase serviceHostBase, Collection < ServiceEndpoint >  endpoints, BindingParameterCollection bindingParameters)
        {
             return ;
        }

         public   void  ApplyDispatchBehavior(ServiceDescription serviceDescription, ServiceHostBase serviceHostBase)
        {
             foreach  (ChannelDispatcher channDisp  in  serviceHostBase.ChannelDispatchers)
            {
                channDisp.ErrorHandlers.Add( this );
            }
        }

         public   void  Validate(ServiceDescription serviceDescription, ServiceHostBase serviceHostBase)
        {
             foreach  (var svcEndpoint  in  serviceDescription.Endpoints)
            {
                 if  (svcEndpoint.Contract.Name  !=   " IMetadataExchange " )
                {
                     foreach  (var opDesc  in  svcEndpoint.Contract.Operations)
                    {
                         if  (opDesc.Faults.Count  ==   0 )
                        {
                             string  msg  =
                                 string .Format( " ServiceErrorHandlerBehavior requires a FaultContract(typeof(ApplicationFault)) on each operation contract. The {0} contains no FaultContracts. " , opDesc.Name);
                             throw   new  InvalidOperationException(msg);
                        }

                        var fcExists  =  from fc  in  opDesc.Faults
                                        where  fc.DetailType  ==   typeof (ReceiverFaultDetail)
                                       select fc;

                         if  (fcExists.Count()  ==   0 )
                        {
                             string  msg  =   string .Format( " ServiceErrorHandlerBehavior requires a FaultContract(typeof(ApplicationFault)) on each operation contract. " );
                             throw   new  InvalidOperationException(msg);
                        }
                    }
                }
            }
        }
    }
}

 

 

只完成上边的代码还不够，由于使用了ExtensionElement所以Config文件里也要相应的配置

App.Config 代码

<? xml version="1.0" encoding="utf-8"  ?>
< configuration >
   < system.web >
     < compilation  debug ="true"   />
   </ system.web >
   <!--  When deploying the service library project, the content of the config file must be added to the host's 
  app.config file. System.Configuration does not support config files for libraries.  -->
   < system.serviceModel >

     <extensions>
       <behaviorExtensions>
         <add name="ServiceErrorHandler" type="WcfServiceLibrary1.ServiceErrorHandlerBehaviorExtensionElement, WcfServiceLibrary1, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" />
       </behaviorExtensions>
     </extensions>
    
     < services >
       < service  behaviorConfiguration ="WcfServiceLibrary1.Service1Behavior"
        name ="WcfServiceLibrary1.MyService" >
         < endpoint  address =""  binding ="wsHttpBinding"  contract ="WcfServiceLibrary1.IMyService" >
           < identity >
             < dns  value ="localhost"   />
           </ identity >
         </ endpoint >
         < endpoint  address ="mex"  binding ="mexHttpBinding"  contract ="IMetadataExchange"   />
         < host >
           < baseAddresses >
             < add  baseAddress ="http://localhost:8731/Design_Time_Addresses/WcfServiceLibrary1/Service1/"   />
           </ baseAddresses >
         </ host >
       </ service >
     </ services >
     < behaviors >
       < serviceBehaviors >
         < behavior  name ="WcfServiceLibrary1.Service1Behavior" >
           <!--  To avoid disclosing metadata information, 
          set the value below to false and remove the metadata endpoint above before deployment  -->
           < serviceMetadata  httpGetEnabled ="True" />
           <!--  To receive exception details in faults for debugging purposes, 
          set the value below to true.  Set to false before deployment 
          to avoid disclosing exception information  -->
           < serviceDebug  includeExceptionDetailInFaults ="False"   />
          <ServiceErrorHandler/>
         </ behavior >
       </ serviceBehaviors >
     </ behaviors >
   </ system.serviceModel >
</ configuration >

 

客户端代码：

 

Client 代码

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using ConsoleApplication1.ServiceReference1;
using System.ServiceModel;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            try
            {
                ServiceReference1.MyServiceClient proxy = new ConsoleApplication1.ServiceReference1.MyServiceClient();
                proxy.GetData(0);
            }
            catch (FaultException < ReceiverFaultDetail >  ex)
            {
                Console.WriteLine(ex.Message);
            }
        }
    }
}

 

 

调试程序可以看出，函数运行的顺序为：

客户端调用服务方法发生异常后，现执行ProvideFault方法，然后执行HandleError方法，客户端收到exception执行Catch。

 

总结下：

 

错误处理策略（1）
• 简单的实现
–从业务逻辑/数据访问层抛出CLR异常
– 在服务层捕捉到异常并且转化为适当的Fault
–使用handler记录未捕捉的异常

错误处理策略（2）
• 带有CLR异常的实现
–从业务逻辑/数据访问层抛出CLR异常
– 将CLR异常声明为Fault
–创建错误处理器（error handler）自动将已知的异
常转换为Fault
–记录未捕捉的异常

错误处理策略（3）
• 可互操作的方法
– 从业务逻辑/数据访问层抛出自定义CLR异常
– 将异常定义为数据契约
– 声明自定义异常类型为Fault
– 创建错误处理器（error handler）将自定义异常转换为Fault
– 记录非自定义异常
• 注意：
– 需要对错误处理策略进行良好的定义
• 中立性