This happened to me when I tried to import a Namespace of an Assembly into my XAML Page:
This sucks: “clr-namespace:My.Sub; assembly=MyAssembly”
This works: “clr-namespace:My.Sub;assembly=MyAssembly”
See the difference? Unbelievable, but there is just a space between the ‘;’ and “assembly”. Sure, it’s not possible to use Trim() during parsing. Or there is another reason I dont know why.