> It seems the intended way to reuse LINQ to XML classes is the annotation 
> feature:
> http://blogs.msdn.com/mikechampion/archive/2006/08/17/705278.aspx

    This seems fine enough. And possibility to "inject methods" through 
extensions seems very helpful as well (an example shown in 
http://blogs.msdn.com/mikechampion/archive/2006/09/10/748408.aspx).
    However after few small code experiments I came to a conclusion that it 
might not be enough. I considered adding classes with SVG DOM-like 
properties as annotations to the XElements. An example is the base IDL 
SVGElement which contains attributes "id" and "xmlbase" (referring to "id" 
element attribute and "xml:base" element attribute). I changed it to an 
SvgElement class with Id and XmlBase properties. But then natural question 
occurs: should those be get only or get/set? In the IDL's SVGElement they 
are get/set (with some restrictions).  If I was to support the setting how 
would I do that? I considered constructing my SvgElement with XElement (to 
which it referrers) given during construction and not only reading 
appropriate data but also storing the XElement to be able latter to set the 
data in setters.
    All fine but what if the user copies XElement? The annotation is not 
copied. (And even if I would find a way to copy it it would still be 
incorrect as internal XElement reference would be to the original XElement.) 
Also if user adds a new XElement to the tree I have very poor means to 
detect it to be able to add appropriate annotation.
    Do you have any suggestions to work around this?

    Adam Badura