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SoapExtension Class

The base class for SOAP extensions for XML Web services created using ASP.NET.

For a list of all members of this type, see SoapExtension Members.

System.Object
   System.Web.Services.Protocols.SoapExtension

[Visual Basic]
MustInherit Public Class SoapExtension
[C#]
public abstract class SoapExtension
[C++]
public __gc __abstract class SoapExtension
[JScript]
public abstract class SoapExtension

Thread Safety

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Remarks

ASP.NET allows a SOAP-related infrastructure to be built by means of an extensibility mechanism. The ASP.NET SOAP extension architecture revolves around an extension that can inspect or modify a message at specific stages in message processing on either the client or the server.

ASP.NET SOAP extensions derive from the SoapExtension class. The GetInitializer and Initialize methods provide alternative mechanisms for initializing the SOAP extension to enhance performance. ProcessMessage is the heart of most SOAP extensions, as the method is called at each stage defined in SoapMessageStage, allowing the SOAP extension to perform the desired behavior of that specific SOAP extension. For SOAP extensions that need to modify the SOAP request or SOAP response, ChainStream provides an opportunity to receive the proposed data to be sent across the wire.

Example

[Visual Basic, C#, C++] The following TraceExtension SOAP extension outputs the SOAP request and SOAP response to a specified file when applied to an XML Web service method. If the following SOAP extension is installed to run with an XML Web service, the ASPNET user account must have permission to write to the directory in which the log file is written.

[Visual Basic] 
Imports System
Imports System.Web.Services
Imports System.Web.Services.Protocols
Imports System.IO

' 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
    Inherits SoapExtension

    Private oldStream As Stream
    Private newStream As Stream
    Private m_filename As String

    ' Save the Stream representing the SOAP request or SOAP response into
    ' a local memory buffer.
    Public Overrides Function ChainStream(ByVal stream As Stream) As Stream
        oldStream = stream
        newStream = New MemoryStream()
        Return newStream
    End Function

    ' 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 Overloads Overrides Function GetInitializer(ByVal methodInfo As _
        LogicalMethodInfo, _
    ByVal attribute As SoapExtensionAttribute) As Object
        Return CType(attribute, TraceExtensionAttribute).Filename
    End Function

    ' The SOAP extension was configured to run using a configuration file
    ' instead of an attribute applied to a specific XML Web service
    ' method.  Return a file name based on the class implementing the Web
    ' Service's type.
    Public Overloads Overrides Function GetInitializer(ByVal WebServiceType As _
      Type) As Object
        ' Return a file name to log the trace information to, based on the
        ' type.
        Return "C:\" + WebServiceType.FullName + ".log"
    End Function

    ' Receive the file name stored by GetInitializer and store it in a
    ' member variable for this specific instance.
    Public Overrides Sub Initialize(ByVal initializer As Object)
        m_filename = CStr(initializer)
    End Sub

    ' If the SoapMessageStage is such that the SoapRequest or SoapResponse
    ' is still in the SOAP format to be sent or received over the network,
    ' save it out to file.
    Public Overrides Sub ProcessMessage(ByVal message As SoapMessage)
        Select Case message.Stage
            Case SoapMessageStage.BeforeSerialize
            Case SoapMessageStage.AfterSerialize
                WriteOutput(message)
            Case SoapMessageStage.BeforeDeserialize
                WriteInput(message)
            Case SoapMessageStage.AfterDeserialize
            Case Else
                Throw New Exception("invalid stage")
        End Select
    End Sub

    ' Write the SOAP message out to a file.
    Public Sub WriteOutput(ByVal message As SoapMessage)
        newStream.Position = 0
        Dim fs As New FileStream(m_filename, FileMode.Append, _
                                 FileAccess.Write)
        Dim w As New StreamWriter(fs)
        w.WriteLine("-----Response at " + DateTime.Now.ToString())
        w.Flush()
        Copy(newStream, fs)
        w.Close()
        newStream.Position = 0
        Copy(newStream, oldStream)
    End Sub

    ' Write the SOAP message out to a file.
    Public Sub WriteInput(ByVal message As SoapMessage)
        Copy(oldStream, newStream)
        Dim fs As New FileStream(m_filename, FileMode.Append, _
                                 FileAccess.Write)
        Dim w As New StreamWriter(fs)

        w.WriteLine("----- Request at " + DateTime.Now.ToString())
        w.Flush()
        newStream.Position = 0
        Copy(newStream, fs)
        w.Close()
        newStream.Position = 0
    End Sub

    Sub Copy(ByVal fromStream As Stream, ByVal toStream As Stream)
        Dim reader As New StreamReader(fromStream)
        Dim writer As New StreamWriter(toStream)
        writer.WriteLine(reader.ReadToEnd())
        writer.Flush()
    End Sub
End Class

' Create a SoapExtensionAttribute for our SOAP Extension that can be
' applied to an XML Web service method.
<AttributeUsage(AttributeTargets.Method)> _
Public Class TraceExtensionAttribute
    Inherits SoapExtensionAttribute

    Private m_filename As String = "c:\log.txt"
    Private m_priority As Integer

    Public Overrides ReadOnly Property ExtensionType() As Type
        Get
            Return GetType(TraceExtension)
        End Get
    End Property

    Public Overrides Property Priority() As Integer
        Get
            Return m_priority
        End Get
        Set(ByVal Value As Integer)
            m_priority = value
        End Set
    End Property

    Public Property Filename() As String
        Get
            Return m_filename
        End Get
        Set(ByVal Value As String)
            m_filename = value
        End Set
    End Property
End Class

[C#] 
using System;
using System.Web.Services;
using System.Web.Services.Protocols;
using System.IO;
using System.Net;

    // 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;
            }
        }
    }

[C++] 
#using <mscorlib.dll>
#using <System.dll>
#using <System.Web.Services.dll>
using namespace System;
using namespace System::Web::Services;
using namespace System::Web::Services::Protocols;
using namespace System::IO;
using namespace System::Net;

public __gc class TraceExtension;

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

private:
   String* filename;
   int priority;
public:
   TraceExtensionAttribute() : filename(S"c:\\log.txt") {}

   __property Type* get_ExtensionType() { return __typeof(TraceExtension); }

   __property int get_Priority() { return priority; }
   __property void set_Priority( int value ) { priority = value; }

   __property String* get_Filename() 
   {
      return filename;
   }
   __property void set_Filename( String* value ) 
   {
      filename = value;
   }

};

// 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 __gc class TraceExtension : public SoapExtension 
{
   Stream* oldStream;
   Stream* newStream;
   String* filename;

public:
   // Save the Stream representing the SOAP request or SOAP response into
   // a local memory buffer.
   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.    
   Object* GetInitializer(LogicalMethodInfo* /*methodInfo*/, SoapExtensionAttribute* attribute) 
   {
      return (dynamic_cast<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.
   Object* GetInitializer(Type* WebServiceType) 
   {
      // Return a file name to log the trace information to, based on the
      // type.
      return String::Format( S"C:\\{0}.log", WebServiceType->FullName );    
   }

   // Receive the file name stored by GetInitializer and store it in a
   // member variable for this specific instance.
   void Initialize(Object* initializer) 
   {
      filename = dynamic_cast<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.
   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(S"invalid stage");
      }
   }

   void WriteOutput(SoapMessage* message)
   {
      newStream->Position = 0;
      FileStream* fs = new FileStream(filename, FileMode::Append,
         FileAccess::Write);
      StreamWriter* w = new StreamWriter(fs);

      String* soapString = (dynamic_cast<SoapServerMessage*>(message)) ? S"SoapResponse" : S"SoapRequest";
      w->WriteLine(S"-----{0} at {1}", soapString,__box(DateTime::Now));
      w->Flush();
      Copy(newStream, fs);
      w->Close();
      newStream->Position = 0;
      Copy(newStream, oldStream);
   }

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

      String* soapString = (dynamic_cast<SoapServerMessage*>(message)) ?
         S"SoapRequest" : S"SoapResponse";
      w->WriteLine(S"-----{0} at {1}", soapString,__box(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();
   }
};

[JScript] No example is available for JScript. To view a Visual Basic, C#, or C++ example, click the Language Filter button Language Filter in the upper-left corner of the page.

Requirements

Namespace: System.Web.Services.Protocols

Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family, .NET Compact Framework

Assembly: System.Web.Services (in System.Web.Services.dll)

See Also

SoapExtension Members | System.Web.Services.Protocols Namespace | SoapMessageStage | SoapExtensionAttribute | LogicalMethodInfo

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