I got a request earlier today to help out with writing a node-binding C# control for InfoPath and I thought I'd share with people the two important parts.

1. Make sure you have the MSXML reference 
      Microsoft XML, v5.0 is what you're looking for in the References dialog (in VS)


2. Make sure you have a binding property which is an MSXML node:

public MSXML5.IXMLDOMNode Value

{

get { return node; }

set { node = value; }

}