WPF Diagramming Library


What free or open source WPF diagramming libraries have you used before? I'm working on my thesis and have no money to pay for the commercial alternatives.

Valid answers should support undo/redo, exporting to XML and hopefully good documentation.

I'm building an open source UML / database diagramming tool.

Best Solution

sukram has a excellent series on CodeProject... it's a MUST READ!