XAML namespace with whitespace in it

It can't be done. Maybe in XAML 2009. In the old one, it just fails. I am using ReSharper and it automatically finds the controls in XAML in the loaded libraries and creates the appropriate namespace. For a library called "My Controls" it adds an "assembly=My Controls" at the end of the clr-namespace and the compilation fails with "Unknown build error".

The only solution I could find for this is to rename the library so that it doesn't have spaces in it. In my case the library was actually another project and I changed the name in the project properties to have underscore rather than space.