MrDave's (David Yack) Blog!

As your Silverlight applications get more sophisticated you might run into a situation where a UI element ends up invoking  a method that uses Isolated Storage.  In our case we were caching some metadata locally to improve performance.  It turns out there’s some compatibility issue with the design surface and Isolated Storage.  You can read more details on the forum thread here.  The solution is to check if your in design mode and if so stay away from Isolated Storage calls.

From Blend you might see this throw an error like the following image:

If you were to attach a debugger to blend you would see what in your code is causing the problem.  In this case it’s the call to File Exists.