title: WPF Diagramming Library
body: <p>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.</p>
  
  <p>Valid answers should support undo/redo, exporting to XML and hopefully good documentation.</p>
  
  <p>I'm building an open source UML / database diagramming tool.</p>