The resource “x” could not be resolved.

Question

I have recently upgraded to VS 2012, I had to as I needed to start using the .net 4.5 but that is besides the point. My problem is the following:

I have a Resource

Answer 1

I had placed some Style in Window.Resources a this caused my problem

After deleting all styles from MainWindow problem disappeared.

Found second problem:

Problem was Platform Target set to x64.

After changing it to AnyCPU the resources in design works..