Type or namespace cannot be found, when reference does exist

Question

I have a wpf Application in which I am trying to reference a class library i have created. I have added a reference to the .dll And i have added the using statement to my fi

Answer 1

Sometimes an explicit naming of the assembly which contains the namespace is required.

xmlns:myns="clr-namespace:MyNamespace;assembly=MyAssembly"

I don't know why it is sometimes required.