We have some custom shapes that we are assigning to the UIElement of a node whenever a user drops one of our shapes onto a diagram.

We are trying to implement an Undo when the user rotates the node, but when we begin recording the action as part of a composite command, we get the following exception:

Unable to cast object of type 'MindFusion.Diagramming.Wpf.DiagramItemProperties' to type 'MindFusion.Diagramming.Wpf.DiagramNodeProperties'

The exception is being thrown in the DiagramNode.SaveProperties().

We are at a loss as to why the cast cannot take place in the SaveProperties() method. Is there anything special that needs to be done to make our node's DiagramItemProperties castable to a DiagramNodeProperties instance? Our code is shown below.

CompositeCmd composite = new CompositeCmd(CurrentDiagram, "RotateObject");






double selectionCount = CurrentDiagram.Selection.Items.Count;



bool unRotatableItems = false;



double unrotatedCount = 0;



foreach (DiagramNode node in CurrentDiagram.Selection.Nodes)



{




if (node.UIElement is IRotatable)




{





ChangeItemCmd c = null ;





try





{






c = new ChangeItemCmd(node as DiagramItem, "Change");





}





catch (Exception ex)





{






Trace.WriteLine(ex);






if (ex.InnerException != null)






{







Trace.WriteLine(ex.InnerException);






}





}





node.RotationAngle = node.RotationAngle + degrees;





(node.UIElement as IRotatable).Angle = node.RotationAngle;






if (c != null)





{






c.Execute();






composite.AddSubCmd(c);





}




}




else




{





unRotatableItems = true;





unrotatedCount++;




}



}



composite.Execute();