StartDrawCommon is a protected virtual method defined in the BehaviorBase class. It implements the following interactions common for all Behavior types, and then calls the StartDraw method to run code specific to each behavior class:

• drawing selection rectangle when ModifierKeyAction.Select modified key is held down;
• moving selected items;
• moving the Diagramview.AutoHandlesItem if ModificationStart is set to AutoHandles;
• adding new link segments if AllowSplitLinks is enabled;

Unless you want to stop any of the common actions above, you should override the StartDraw method instead. E.g. of the built-in behavior types, only SelectOnlyBehavior overrides StartDrawCommon to prevent all but the draw-selection operation.

I hope that helps,
Stoyan

You can find a custom behavior class and custom node modifications shown in the Fishbone diagram sample project. The StartDraw method only selects what object will be modified and returns an InteractionState wrapping it. Next mouse movements will lead to calling UpdateModify on that object. You could also override the behavior's OnMouseMove method if you prefer implementing all interaction logic without creating custom node classes.

If you have the source code, I suppose you could build your custom interaction logic directly into the library's standard classes, to spare yourself from having to derive new classes and override methods.

I hope that helps,
Stoyan

Thanks for reply.
I reviewed the sample, it is a pretty good sample to show something. But there still is a question. These track shapes are node shape, are not a link shape. Dependence on my experience there are 2 cases.

Case 1
when users drag the first point or the end point of a link then StartDraw method will be called.
Case 2
If users drag any other point else of a link then MouseMove method will called.

How to do something let StartDraw method can be called in Case 2 ?
Thanks a lot.