WPF, ‘Object reference not set to an instance of an object’ in Designer
What Alex says is the way to go. But I think its a little confusing to understand what he is saying. Assuming you have your project open in Visual Studio, open another Visual Studio instance and select Debug->Attach To Process. In the dialog which opens select XDesProc.exe (which is the XAML UI Designer) for VS2012 … Read more