For Xml Statements Behave Differently Under MSDTC

I have SQL stored proc that calls a CLR function. This function does a "select ... for xml" statement, manipulates the XML a little, and returns the manipulated XML to the stored proc.

This all works fine when I call the stored proc from a query window, but when I have BizTalk call the stored proc, the CLR function fails. I have a feeling this may have to do with BizTalk using MSDTC , but I am not sure.

Here's a code snippet from where CLR function fails:

SqlConnection conn = new SqlConnection("Context Connection=true");
conn.Open();SqlCommand cmd = new SqlCommand("Select * From Items FOR XML AUTO",conn);XmlDocument xdoc = new XmlDocument();xdoc.Load(cmd.ExecuteXmlReader());

Under BizTalk, the last line fails with: System.InvalidOperationException "Invalid command sent to ExecuteXmlReader. The command must return an Xml result."

Now to see why XmlReader doesn't like the returned data, i changed the last 2 lines of that snippet to this:
SqlDataReader dr = cmd.ExecuteReader();

dr.Read();Object obj = dr[0];



If i have a breakpoint after that last line, obj is of type string when i call the proc myself, but it is a byte[] under Biztalk. If i look at the bytes themselves, its close to the expected xml...but with some nontext bytes sprinkled around. I can't seem to cast or encode the byte array into anything useful.

Anyone have any idea what is going on here? Why would the same code return different types based on a) who is calling it, or b) the type of transaction used?

Thanks,
Ron