Designer not loading while attempting to run a WP7 mango app in WP8

Question

I have a published Windows Phone 7.5 (Mango app). Since the windows phone 8 tools are available, I tried to run the project in Microsoft Visual Studio Express 2012 for Windows Phone. The app runs in all emulators and the Windows Phone 7 device. The problem I'm facing is that the the designer is not displayed, the xaml file can be seen but the UI is not displayed.

Instead an error is displayed saying System.NullReferenceException

Object reference not set to an instance of an object. at Microsoft.Expression.DesignHost.Isolation.Remoting.STAMarshaler.WaitForCompletion(NestedCallContext nestedCallContext, BlockingCall call, WaitHandle timeoutSignal)

But it is displayed in Blend for Visual Studio. What could be wrong?

Answer 1

Apparently this question has been trolling in the Microsoft forums. Few solutions were mentioned there which included uninstalling and reinstallinf win WP8 SDK.

I did none of these, I checked for updates for Visual Studio and found one. The installation took some time, but it did fix the designer issue!! :D