Currently, the RadDiagram control does not have a bi-directional MVVM mechanism (when using GraphSource). This means, that any shapes or connections cannot be added through its UI.
However, for Q2 2012, we are planning to release such mechanism, which will notify the underlying itemssource for these changes, so that it can be properly updated. It will represent an extended IGraphSource interface with couple of additional methods. This graph source would be responsible for creating new models, adding and removing them from the underlying collections.
Moreover, we are working on similar approach for serialization and deserialization.
Please share with us any feedback on this approach or suggestions, if you have any.
the Telerik team
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