>Hmmm. Works for me. Given this file in a project named Members:

namespace Members.Library
>{
>    public class Class1
>    {
>    }
>}

>then the following WPF XAML shows the Library.Members namespace in Intellisense and ends up like this:

<Window x:Class="WpfApplication1.Window1"
>    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
>    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
>    xmlns:Members="clr-namespace:Members.Library;assembly=Members" >
></Window>

I just tried something similar and it worked in the test (well the intellisense didn't show me what I expected) and the error does not show up. This is really weird. Maybe I need to start everything over from scratch? Aargh, this is really frustrating.