VS 2010 - How To Create New Object Type

I don't know if I stated what I mean in the subject correctly, but I'm making a parsing engine similar to XML so I can implement it in my programs. What I need to know is how to make a new thing like how with XML you can declare a new XMLDocument, like
Dim XDoc as new XDocument
OR:
Dim NPoint as New Point(10,35)

With my parsing engine, I'll have a document type called EDocument and I want to be able to declare string as an EDocument like this
Dim MyDoc as New EDocument()