Dockable ans resizable WPF window like the scene explorer

Hi everyone

Lately, I went on c# and WPF to create nice UI.
Now, I'd like to create a dockable UI that is resizable when it's docked (like the scene explorer in max 2015) but I didn't succeed for now.

Using the 3ds max .net help (http://help.autodesk.com/view/3DSMAX/2015/ENU/?guid=__files_GUID_F5FF528..., Creating Dockable UI or new Extended Viewports using .NET section), I managed to be able to see my Window inside the customize menu, but as soon as I lunch it, it crash Max...

To get there, I created 2 class, a wpf window class named MainWindow and the CuiDockableContentAdapter class with this:

public override Type ContentType
{
get { return typeof(MainWindow);
}

public override object CreateDockableContent()
{
return new MainWindow();
}

Can anyone help me on this one ?