Category: BizTalk

Richard Hallgren recently blogged about how to remove Xml namespaces from Xml documents, as has Kirk Allen Evans earlier here and here. While the latter writes from a general .NET and ASP.NET perspective Richard’s post is from a BizTalk perspective and in his post he asks for alternative ways, other then the ways he is presenting, of doing it. 

The root issue is how do I turn

<ns0:Blah xmlns:ns0=”http://RemoveXmlNamespace.BTS.BlahMessage”>

into

<Blah>

First of all, let me just say that I understand namespace and I don’t think they should be removed if at all avoidable. This is not my first choice of a solution, as it probably isn’t for anyone working with BizTalk. The fact remains though that in some cases it still turns out to be necessary. My option of doing this would then be by using a pipeline component and the classes available to us from Microsoft.BizTalk.Streaming.dll. My main reason for this is performance. I would really hate to have to keep either the source document or the resulting document in memory using XmlDocument and MemoryStream like the XslTransform pipeline component sample from the BizTalk Server 2006 SDK does. I’m pretty certain that particular sample can be enhanced using XPathDocument, XslCompiledTransform and VirtualStream (to keep down the impact on memory) but it still isn’t as good if your only purpose is removing the namespace. That sample can however do many other things that my option can’t, since it does an XslTransform and this doesn’t.

So using the streaming classes in general and XmlTranslatorStream in particular we can override some of it’s methods to create a streaming xsl transformation doing what we want. The resulting code is suprisingly simple. Here is the Execute method:

public Microsoft.BizTalk.Message.Interop.IBaseMessage Execute(

    IPipelineContext pContext,

    Microsoft.BizTalk.Message.Interop.IBaseMessage pInMsg)

{

    pInMsg.BodyPart.Data = new XmlNamespaceRemoverStream(

        pInMsg.BodyPart.GetOriginalDataStream());

    return pInMsg;

}

And here is the class that does the actual work (although as you can see it doesn’t really do much):

public class XmlNamespaceRemoverStream : XmlTranslatorStream

{

    protected override void TranslateStartElement(

        string prefix, string localName, string nsURI)

    {

        base.TranslateStartElement(null, localName, null);

    }

    protected override void TranslateAttribute()

    {

        if (this.m_reader.Prefix != “xmlns”)

            base.TranslateAttribute();

    }
    public XmlNamespaceRemoverStream(Stream input)

        : base(new XmlTextReader(input), Encoding.Default)

    { }

}

This sample is available for download: removexmlnamespacepipeline.zip.

I previously experienced an issue with a general purpose (not an assembler/disassembler) consuming pipeline component in BizTalk Server 2006. For those of you unfamilliar with the term a consuming pipeline component is just that, a component that consumes the messages and returns null to stop pipline and message processing. Having tested this on R2 I’m happy to report that this issue doesn’t exist any more.

In short, my previous issue was that in some situations a consuming pipeline component might cause an endless loop to occur within BizTalk, which in any scenario is undesirerable. The cause of this was if the pipeline threw an exception making the message become suspended on the first time around, and then returned null the second time around. Granted, not a very common scenario, so chances are good that it might not have happened to you.

This code in the execute method of the pipeline component would allow you to reproduce the error:

public IBaseMessage Execute(IPipelineContext pContext, IBaseMessage pInMsg)

{

    if (pInMsg.MessageID != new Guid((string)pInMsg.Context.Read(

        “InterchangeID”, “http://schemas.microsoft.com/BizTalk/2003/system-properties”)))

    {

        System.Diagnostics.Trace.WriteLine(“EndLess: Return null”);

        return null; // resume, return null

    }

    else

    {

        System.Diagnostics.Trace.WriteLine(“Ex”);

        throw new Exception(“First time in pipeline, throwing exception”);

    }

    return pInMsg;

}

Just stick this code in the appropriate place in the custom pipeline component, create a receive pipeline, and run a message though. First time around it will get suspended. Now go ahead and resume it. Wham! There you go – endless loop in 2006. However like I said, R2 does not display this behavior, and with any luck some hotfix or update for 2006 might contain the fix as well.

The code above also shows another small trick: How to know if a message is a resume in a receive pipeline. When a message is first received the MessageID and InterchangeID are the same, however on a receive the MessageID will be a new one, but the InterchangeID will remain the same as it was the first time.