用asp.net2 开发SoapExtension所出现的问题

using  System;
using  System.Web.Services;
using  System.Web.Services.Protocols;
using  System.IO;
using  System.Net;

namespace  TraceExtension
{
     //  Define a SOAP Extension that traces the SOAP request and SOAP
     //  response for the XML Web service method the SOAP extension is
     //  applied to.

     public   class  TraceExtension : SoapExtension
    {
        Stream oldStream;
        Stream newStream;
         string  filename;

         //  Save the Stream representing the SOAP request or SOAP response into
         //  a local memory buffer.
         public   override  Stream ChainStream(Stream stream)
        {
            oldStream  =  stream;
            newStream  =   new  MemoryStream();
             return  newStream;
        }

         //  When the SOAP extension is accessed for the first time, the XML Web
         //  service method it is applied to is accessed to store the file
         //  name passed in, using the corresponding SoapExtensionAttribute.    
         public   override   object  GetInitializer(LogicalMethodInfo methodInfo, SoapExtensionAttribute attribute)
        {
             return  ((TraceExtensionAttribute)attribute).Filename;
        }

         //  The SOAP extension was configured to run using a configuration file
         //  instead of an attribute applied to a specific XML Web service
         //  method.
         public   override   object  GetInitializer(Type WebServiceType)
        {
             //  Return a file name to log the trace information to, based on the
             //  type.
             return   " C:/ "   +  WebServiceType.FullName  +   " .log " ;
        }

         //  Receive the file name stored by GetInitializer and store it in a
         //  member variable for this specific instance.
         public   override   void  Initialize( object  initializer)
        {
            filename  =  ( string )initializer;
        }

         //   If the SoapMessageStage is such that the SoapRequest or
         //   SoapResponse is still in the SOAP format to be sent or received,
         //   save it out to a file.
         public   override   void  ProcessMessage(SoapMessage message)
        {
             switch  (message.Stage)
            {
                 case  SoapMessageStage.BeforeSerialize:
                     break ;
                 case  SoapMessageStage.AfterSerialize:
                    WriteOutput(message);
                     break ;
                 case  SoapMessageStage.BeforeDeserialize:
                    WriteInput(message);
                     break ;
                 case  SoapMessageStage.AfterDeserialize:
                     break ;
                 default :
                     throw   new  Exception( " invalid stage " );
            }
        }

         public   void  WriteOutput(SoapMessage message)
        {
            newStream.Position  =   0 ;
            FileStream fs  =   new  FileStream(filename, FileMode.Append,
                FileAccess.Write);
            StreamWriter w  =   new  StreamWriter(fs);

             string  soapString  =  (message  is  SoapServerMessage)  ?   " SoapResponse "  :  " SoapRequest " ;
            w.WriteLine( " ----- "   +  soapString  +   "  at  "   +  DateTime.Now);
            w.Flush();
            Copy(newStream, fs);
            w.Close();
            newStream.Position  =   0 ;
            Copy(newStream, oldStream);
        }

         public   void  WriteInput(SoapMessage message)
        {
            Copy(oldStream, newStream);
            FileStream fs  =   new  FileStream(filename, FileMode.Append,
                FileAccess.Write);
            StreamWriter w  =   new  StreamWriter(fs);

             string  soapString  =  (message  is  SoapServerMessage)  ?
                 " SoapRequest "  :  " SoapResponse " ;
            w.WriteLine( " ----- "   +  soapString  +
                 "  at  "   +  DateTime.Now);
            w.Flush();
            newStream.Position  =   0 ;
            Copy(newStream, fs);
            w.Close();
            newStream.Position  =   0 ;
        }

         void  Copy(Stream from, Stream to)
        {
            TextReader reader  =   new  StreamReader(from);
            TextWriter writer  =   new  StreamWriter(to);
            writer.WriteLine(reader.ReadToEnd());
            writer.Flush();
        }
    }

     //  Create a SoapExtensionAttribute for the SOAP Extension that can be
     //  applied to an XML Web service method.
    [AttributeUsage(AttributeTargets.Method)]
     public   class  TraceExtensionAttribute : SoapExtensionAttribute
    {

         private   string  filename  =   " c:/log.txt " ;
         private   int  priority;

         public   override  Type ExtensionType
        {
             get  {  return   typeof (TraceExtension); }
        }

         public   override   int  Priority
        {
             get  {  return  priority; }
             set  { priority  =  value; }
        }

         public   string  Filename
        {
             get
            {
                 return  filename;
            }
             set
            {
                filename  =  value;
            }
        }
    }


}

using  System;
using  System.Web;
using  System.Collections;
using  System.Web.Services;
using  System.Web.Services.Protocols;
using  System.IO;



///   <summary>
///  WebService 的摘要说明
///   </summary>
[WebService(Namespace  =   " http://www.lanbridge.net/ " )]
[WebServiceBinding(ConformsTo  =  WsiProfiles.BasicProfile1_1)]
public   class  WebService : System.Web.Services.WebService {

     public  WebService () {

         // 如果使用设计的组件，请取消注释以下行 
         // InitializeComponent(); 
       
    }

    [WebMethod]
    [TraceExtension.TraceExtension(Filename  =   " C:/data.xml " ,Priority = 1 )]
     public   string  HelloWorld( string  v) {                
         return  v + " asdf " ;
    }
    

}

　 < webServices >
       < soapExtensionTypes >         
         < add  type ="TraceExtension.TraceExtension,TraceExtension"  priority ="1"   group ="High"    />
       </ soapExtensionTypes >
     </ webServices >