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The above video shows the great XAMLSPY tool which is a massively helpful tool when working with any XAML based application, like a Windows Store app. XAMLSpy allows you to get insights such as performance & memory usage but for me the real value is when you add it to the application you get a set of small tools to use in the app to help identify and navigate the XAML.
Once you have found the piece of XAML that is causing issues, you can test out your ideas in real time using the real time editor functions which really speeds up development. This is a must have tool for those who really have pride in their craft!