Having a problem with an Xlang Null Exception

I’ve
created a BizTalk Server 2009 application set with a two way Receive
port.  The orchestration goes like this:

1:
The incoming Message is Received via an HTTP Pipeline

2:
When the message comes in, I have a “Decide” shape, where the two
promoted fields “Username/Password” in the message are checked
against a SQL Server data store.  If the user’s credentials succeed or
fail, a Message is created (using an Message Assignment I explain in step 3)
saying “Success” or “Failed” and sent back to the sender.

3: 
For both the SQL Query for the user’s credentials and the means to instantiate
a Message Assignment, I use a custom C# class library.  (I’ll eventually
learn the  BizTalk data adapter for SQL Queries, but for now it seems to
work great.).  As my current tests are using invalid user credentials, I
just want a “Failed” message created, and sent back.  And while
I know I’m getting the SQL Check just fine, I know it’s the Message Assignment
for the “Failed” message where I’m falling into this error:

Shape
name: CreateFailureMessage (The message that I send if a User doesn’t
authenticate in

ShapeId:
6c9071f5-bcde-489a-90e7-f142310e5c0a

Exception
thrown from: segment 1, progress 17

Inner
exception: Object reference not set to an instance of an object.

The
method that I’m using in particular as to how I’m doing Message Assignment came
from this blog:

http://geekswithblogs.net/michaelstephenson/archive/2006/09/26/92363.aspx  
I used his tutorial practically “as is”. I turned my .xsd into a C#
class via xsd.exe and then created the Adapter class as in his blog. Here’s the
code for that.

namespace
Blaxo.Objects

{

   
[Serializable]

   
[XmlRoot(“Response”, Namespace = “http://BTPing.PingReply“)]

   
public class PingReplyAdapter : Response

   
{

       
public XmlDocument ToXmlDocument()

       
{

           
XmlSerializer serializer = new XmlSerializer(typeof(PingReplyAdapter));

           
StringBuilder sb = new StringBuilder();

           
serializer.Serialize(new StringWriter(sb, CultureInfo.InvariantCulture),this);

           
XmlDocument doc = new XmlDocument();

           
doc.LoadXml(sb.ToString());

           
return doc;

       
}

   
}

}

The
only thing that I’m wondering after done even more looking into this:

A:
The name space is the name of the .xsd message file.  (PingReply.xsd)

B:
The name of the actual class is the Root node (Reply.cs, as the Root node of
PingReply.xsd is Reply)

So,
perhaps XmlRoot(“Repose”… May need something different?