this will probably be difficult to nail down
unless some inhibitor/check can help within the MouseUp & InteractionState...

i have a small diagram with 6 nodes and generate only 1 link that shows to-from arrow when mouseover is over the next node then the selected one, and when wild clicking around i sometimes get:

at MindFusion.Diagramming.Wpf.InteractionState.IsAllowed(Point point)
at MindFusion.Diagramming.Wpf.Behaviors.BehaviorBase.OnMouseUp(Point mousePosition, MouseButton mouseButton)
at MindFusion.Diagramming.Wpf.Diagram.AN(MouseButtonEventArgs A, Point B)
at MindFusion.Diagramming.Wpf.Diagram.OnPreviewMouseUp(MouseButtonEventArgs e)
at System.Windows.UIElement.OnPreviewMouseUpThunk(Object sender, MouseButtonEventArgs e)
at System.Windows.Input.MouseButtonEventArgs.InvokeEventHandler(Delegate genericHandler, Object genericTarget)
at System.Windows.RoutedEventArgs.InvokeHandler(Delegate handler, Object target)
at System.Windows.RoutedEventHandlerInfo.InvokeHandler(Object target, RoutedEventArgs routedEventArgs)
at System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised)
at System.Windows.UIElement.RaiseEventImpl(DependencyObject sender, RoutedEventArgs args)
at System.Windows.UIElement.RaiseTrustedEvent(RoutedEventArgs args)
at System.Windows.UIElement.RaiseEvent(RoutedEventArgs args, Boolean trusted)
at System.Windows.Input.InputManager.ProcessStagingArea()
at System.Windows.Input.InputManager.ProcessInput(InputEventArgs input)
at System.Windows.Input.InputProviderSite.ReportInput(InputReport inputReport)
at System.Windows.Interop.HwndMouseInputProvider.ReportInput(IntPtr hwnd, InputMode mode, Int32 timestamp, RawMouseActions actions, Int32 x, Int32 y, Int32 wheel)
at System.Windows.Interop.HwndMouseInputProvider.FilterMessage(IntPtr hwnd, WindowMessage msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
at System.Windows.Interop.HwndSource.InputFilterMessage(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
at MS.Win32.HwndWrapper.WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
at MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o)
at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
at MS.Internal.Threading.ExceptionFilterHelper.TryCatchWhen(Object source, Delegate method, Object args, Int32 numArgs, Delegate catchHandler)

any ideas/tips please?

cheers Ulthien

Actually, just figured out this happens ONLY if the single DiagramLink is visible...

so the event handling when links are visible goes somehow broke if the user clicks too quick around.

What is the type of that exception, and what do you mean by generating a link? I suppose you could get an exception if the link is deleted after the control started tracking interaction state for its modification - e.g. while wild-clicking you select the link, start dragging an adjustment handle, then delete the link before dropping the handle.

Try setting link.Locked = true, or set e.Cancel from the LinkStartModifying handler.

I hope that helps,
Stoyan