Flowchart Control for WPF

I need to design a control that can create/manipulate a really simple Algorithm flow chart. It will only have conditional (if, if,else) and assignment blocks. Some key features that I need to implement are: - Users can freely add/manipulate/remove conditional and statement blocks on anywhere desired. - The chart can be folded/expanded. (For instance, if I clicked on the plus button right below b=3 assignment statement, everything below would be folded) Are there any non-proprietary controls available for .NET that I can use? If not, what are some strategies that I should employ to tackle this problem?