vs2010 Custom MarkupExtension

Question

Hi,

We have just switched to vs2010 from vs2008, and our projects compile and run well without any problem. However, the xaml designer has some errors. Here is one of the errors hope someone can provide a solution.

We have a custom MarkupExtension, and we use it in xaml to get certain resources. Something like this:

<Button Style="{l:GetResource Key=MyButtonStyle}" />

I know we can use StaticResource or DynamicResource. However we have our reasons to use the custom markupextension.

The error message from the designer is:

'GetResourceExtension' is not valid for Setter.Value. The only supported MarkupExtension types are DynamicResourceExtension and BindingBase or derived types.

My question is that the code works fine in vs2008, and also runs fine in 2010, how to make the 2010 desinger work?

Thanks,

Q