I have the same problem as here
Assembly reference not found in XAML, but code compiles when referenced in xaml.cs class
but I don't understand what he means in answer: "Adding the solution itself to the reference path of the assembly solves the problem! ".
I downloaded Example project too from WPF.MDI project web page and it works fine. I use VS 2012 and.Net 4.5 on Win 8. Can someone explain me in details what i have to do in VS? Thanks