SoapExtension for Logging Soap Exceptions

using System;
using System.Web;
using System.Web.Services;
using System.Web.Services.Protocols;
using System.IO;
using System.Xml;
using MIT.BizServices.MCUtil.Misc;

namespace MIT.Common.ExceptionHandlingSoapExtension
{
//

// SOAP extension to transfer full exception information from
// server to client in the event of an exception being thrown
// from a webmethod
//

//
// In the event of an exception being thrown during the execution
// of a webmethod on the server, this class steps in and writes detailed
// exception information to the output stream.
//
// Client side, if an exception is detected on the response from a
// webmethod call, this class retrieves the detailed exception
// information from the input stream and throws an exception
// containing the detailed information
//
public class ExceptionHandlingSoapExtension : SoapExtension
{

region "Initialisation methods - not used because this class has no state to maintain"
public override object GetInitializer(System.Type serviceType) {
return null;
}

public override object GetInitializer(System.Web.Services.Protocols.LogicalMethodInfo methodInfo, System.Web.Services.Protocols.SoapExtensionAttribute attribute) {
return null;
}

public override void Initialize(object initializer)
{
}
endregion

region "Stream chaining code"
private Stream oldStream;
private Stream newStream;

public override Stream ChainStream(Stream stream) {
oldStream = stream;
newStream = new MemoryStream();
return newStream;
}

//

// Copies the contents of one stream to another
//

private void StreamCopy(Stream source, Stream dest) {
StreamReader Reader = new StreamReader(source);
StreamWriter Writer = new StreamWriter(dest);
Writer.WriteLine(Reader.ReadToEnd());
Writer.Flush();
}
endregion

public override void ProcessMessage(System.Web.Services.Protocols.SoapMessage message)
{
switch (message.Stage)
{
case SoapMessageStage.BeforeSerialize:
return;

case SoapMessageStage.AfterSerialize:
//If exception present in message, write details
//to the new stream
if (message.Exception != null)
{
InsertExceptionDetails(message.Exception);
}

//Copy new stream to old stream
newStream.Position = 0;
StreamCopy(newStream, oldStream);
return;

case SoapMessageStage.BeforeDeserialize:
//Copy old stream to new stream
StreamCopy(oldStream, newStream);
newStream.Position = 0;
return;

case SoapMessageStage.AfterDeserialize:
//If exception present in message,
//get details from stream and throw to caller
if (message.Exception != null)
{
CheckExceptionDetails();
}
return;

default:
throw new ArgumentException("Invalid message stage");

}
}

//

// Insert details of the specified exception into the output stream

// <param name="ex">Exception to write details for
private void InsertExceptionDetails(Exception ex) {
//Read output stream into XML document
newStream.Position = 0;
XmlTextReader Reader = new XmlTextReader(newStream);
XmlDocument MessageDoc = new XmlDocument();
MessageDoc.Load(Reader);

XmlNamespaceManager NsMgr = new XmlNamespaceManager(MessageDoc.NameTable);
NsMgr.AddNamespace("soap", "http://schemas.xmlsoap.org/soap/envelope/");

//Construct string describing exception
string ErrorInfo;
if (ex.InnerException != null)
{
ErrorInfo = ex.InnerException.Message;
}
else
{
ErrorInfo = ex.Message;
}
//log exception to flat file
Helper.LogException(string.Empty, ex);

//Find existing soap:Fault node describing exception
XmlNode ExceptionNode;
ExceptionNode = MessageDoc.SelectSingleNode("//soap:Fault", NsMgr);

//Add extended exception detail node to Fault node
XmlElement ExceptionDetail;
ExceptionDetail = MessageDoc.CreateElement("ExtendedExceptionDetails");

ExceptionDetail.InnerText = ErrorInfo;

ExceptionNode.AppendChild(ExceptionDetail);

//Write XML document back to output stream
newStream = new MemoryStream();
MessageDoc.Save(newStream);
}

//

// Reads extra exception information from stream

// Details of any exception detail found in the input stream
private void CheckExceptionDetails()
{
//Read input stream into XML document
newStream.Position = 0;
XmlTextReader Reader = new XmlTextReader(newStream);
XmlDocument MessageDoc = new XmlDocument();
MessageDoc.Load(Reader);

XmlNamespaceManager NsMgr = new XmlNamespaceManager(MessageDoc.NameTable);
NsMgr.AddNamespace("soap", "http://schemas.xmlsoap.org/soap/envelope/");

//Find extended exception detail node
XmlNode ExceptionDetailNode;
ExceptionDetailNode = MessageDoc.SelectSingleNode("//soap:Fault/ExtendedExceptionDetails", NsMgr);
XmlNode exception = MessageDoc.SelectSingleNode("//soap:Fault/faultstring", NsMgr);

//Return detail text if found, empty string otherwise
if (ExceptionDetailNode != null)
{
if (exception != null)
{
if (exception.InnerText.Contains("WebServiceException"))
{
throw new WebServiceException(ExceptionDetailNode.InnerText);
}
else
{
throw new Exception(ExceptionDetailNode.InnerText);
}
}
}
}
}
}