The 'clr-namespace' URI refers to a namespace that is not included in the assembly

Question

I\'m trying to include in my XAML some classes which convert values. However, I\'m getting the following error when I compile:

Undefined CLR namespac

Answer 1

Check that your build configuration has the Project selected for build in your current (Active) build configuration.

I just had this problem after fiddling with the Build architecture (from x86 to x64) and the main wpf project had been de-selected.