How to capture XML when calling web service from win apps

in my solution i have three project. one is web service (ASMX), another is win form apps from where i am calling the web service. another class library where class has been design extending SoapExtension class.

my objective is to capture response & request xml when i am calling web service from my win form apps.i am getting object reference not set error when i am trying to capture xml.
here is my class library source code.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Web.Services;
using System.Web.Services.Protocols;
using System.IO;
using System.Net;
using System.Xml;

namespace SoapLogger
{
public class TraceExtension : SoapExtension
{
    private Stream oldStream;
    private Stream newStream;

    private static XmlDocument xmlRequest;
    ///

    /// Gets the outgoing XML request sent to PayPal
    ///

    public static XmlDocument XmlRequest
    {
        get { return xmlRequest; }
    }

    private static XmlDocument xmlResponse;
    ///

    /// Gets the incoming XML response sent from PayPal
    ///

    public static XmlDocument XmlResponse
    {
        get { return xmlResponse; }
    }

    ///

    /// 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;
    }

    ///

    /// If the SoapMessageStage is such that the SoapRequest or
    /// SoapResponse is still in the SOAP format to be sent or received,
    /// save it to the xmlRequest or xmlResponse property.
    ///

    ///
    public override void ProcessMessage(SoapMessage message)
    {
        switch (message.Stage)
        {
            case SoapMessageStage.BeforeSerialize:
                break;
            case SoapMessageStage.AfterSerialize:
                xmlRequest = GetSoapEnvelope(newStream);
                CopyStream(newStream, oldStream);
                break;
            case SoapMessageStage.BeforeDeserialize:
                CopyStream(oldStream, newStream);
                xmlResponse = GetSoapEnvelope(newStream);
                break;
            case SoapMessageStage.AfterDeserialize:
                break;
        }
    }

    ///

    /// Returns the XML representation of the Soap Envelope in the supplied stream.
    /// Resets the position of stream to zero.
    ///

    ///
    ///
    private XmlDocument GetSoapEnvelope(Stream stream)
    {
        XmlDocument xml = new XmlDocument();
        stream.Position = 0;
        StreamReader reader = new StreamReader(stream);
        xml.LoadXml(reader.ReadToEnd());
        stream.Position = 0;
        return xml;
    }

    ///

    /// Copies a stream.
    ///

    ///
    ///
    private void CopyStream(Stream from, Stream to)
    {
        TextReader reader = new StreamReader(from);
        TextWriter writer = new StreamWriter(to);
        writer.WriteLine(reader.ReadToEnd());
        writer.Flush();
    }
    #region NoOp
    ///

    /// Included only because it must be implemented.
    ///

    ///
    ///
    ///
    public override object GetInitializer(LogicalMethodInfo methodInfo,
        SoapExtensionAttribute attribute)
    {
        return null;
    }

    ///

    /// Included only because it must be implemented.
    ///

    ///
    ///
    public override object GetInitializer(Type WebServiceType)
    {
        return null;
    }

    ///

    /// Included only because it must be implemented.
    ///

    ///
    public override void Initialize(object initializer)
    {
    }
    #endregion NoOp
}
}

here i will show how i am calling web service from win apps

    private void button1_Click(object sender, EventArgs e)
    {

        using (ServiceRef.TestServiceSoapClient oService = new ServiceRef.TestServiceSoapClient())
        {
            textBox1.Text = oService.HelloWorld("Sudip");
            var soapRequest = SoapLogger.TraceExtension.XmlRequest.InnerXml;
            var soapResponse = SoapLogger.TraceExtension.XmlResponse.InnerXml;
        }
    }

this two line is giving object reference error

            var soapRequest = SoapLogger.TraceExtension.XmlRequest.InnerXml;
            var soapResponse = SoapLogger.TraceExtension.XmlResponse.InnerXml;

i just could not figure out why i am getting error.

in win form apps has one app.config where i register my class library assembly to capture the xml. here is my app.config details




   
       
           
       
   
   
       
   





 
   
 


   


when i search google just to know how to capture request/response xml then i got this kind of many article. i followed many but nothing works.

this url i followed to get the job done http://jramirezdev.net/blog/c-tip-capturar-los-mensajes-soap-de-un-servicio-asmx-que-hemos-referenciado

what kind of mistake i am making not clear. i set the break point at every method in my class library method but when web service call no method got executed in the class library. i dont want to use any tool like wireshark,fiddler to capture the request/response xml rather want to do same thing programatically.

so please guide me what is my mistake. why i am getting object reference not set error. please have a look at my code or go to the url link and tell me what is wrong in my approach.