title: restricting the size of wpf dockpanel region
body: <p>Is there a way you can pin a wpf dockpanel?   I have searched on the net and I have not found any functionality that will allow this.  What I want is to lock the size of a dockpanel's dock regions.  For example I want the right region"s width to stay locked all the time.  The only solutions to this that I have seen are 3rd party controls.  Does anyone know of a way to restrict the width of these regions?  Thanx in advance.</p>