VS2012/ Blend 5: Debugging an Exception (only) occurring in design view
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I'm developing a Metro-style app (for Windows 8) using C# and XAML. I have set up my viewmodels to be used as design-time datacontexts, like so:

    xmlns:vm="using:hub.ViewModels"
    d:DataContext="{d:DesignInstance IsDesignTimeCreatable=True, Type=vm:ViewModels

My app appears to work perfectly when run, but in the design views of both VS 2012 and Blend, I occasionally get this (unhelpful) error message:

    An Exception was thrown. TargetException: Error in the application.
    Stacktrace
    at System.ComponentModel.PropertyChangedEventHandler.Invoke(Object sender, PropertyChangedEventArgs e)
    InnerException: None

This *only* happens in the design view - meaning I can't set breakpoints around all my INotifyPropertyChanged() events.

What is the best approach to debugging design-time errors?
