.net Plugin Viewport update issues.

Hello,

I had developed a plugin with C# max SDK and Visual Studio (for Max 2013), everything work fine, but I have to select some nodes in the wiewport and add them to a ListBox here also everything is ok, except the fact that when my Form (floating form) is open there are some issues with view port display...
I mean : I cant see my selection square (when you click and drag to select), also when I move or select a node the viewport don't update immediately ...

Like it mentioned in the Max SDK help I use a Form derived from a MaxForm. It seem to be ok because when I start my plugin I can see that the Form's icon is a 3dsmax icone not a DotNet icone...

Iam stuck, and .NET SDK help is very short.

May be some one have a lead to solve this issues?

Thank you very much!

(I didn't see others post on scriptSpot about C# or C++ plug-in development maybe it's not the right place to ask for it?)