Expander doesn’t show content at design time in Visual Studio 2010

I have a custom template for an expander that works correctly in VS 2008. In VS 2010 the expander works at runtime but won’t expand at design time. I suspected a binding change in the 2010 template but have been unable to find a copy. To test this theory
I downloaded Blend, made a copy of the standard template, then pasted the xaml into 2010. The Blend template duplicates the problem I have with my custom template.

I have already read the articles about not setting heights and widths but these aren’t the problem. To duplicate simply copy the xaml from Blend as I did.

What has changed between 2008 and 2010?

Hi 8xFather,It is hard to find the cause without any code, could you please provide some code which can repro this issue in VS 2010?  Visual Studio 2010 improve many things in the XAML designer, for details you could refer to this link:

Bob,Thanks for the reply and any help is greatly appreciated as we use this control heavily in several of our projects.Here is the code for my custom expander  but like i said above you can also duplicate the problem by copying the expander template from Blend to a VS 2010 project.

Hi 8xFather,I copied the code in VS2010 and the control can display in the VS 2010 designer.