XML document or XML Node is not serailizable.
so the rule of thumb in biztalk is that only serlizable types can be used in orchestrations with long running types and if you require to non serailizable type use them within a Atomic scope.
Now comes the interesting part xmldocument and xmlnode : if you create variable of type xmlnode , you will come across the following exception:
a non-serializable object type ‘System.Xml.XmlNode varXmlNode’ can only be declared within an atomic scope or service
but if you create a xmldocument variable the above error is no thrown why? BizTalk engine by default serailizes xmldocument….