Designer rejecting DataTemplate.DataType

Question

I am try to fit some WPF into my current Windows Forms application. When I use this simple user control, the designer for that control does not reload.

This only happens in this application. If I make a clean Windows Forms project, add these files, the designer works fine.

I have tried a reload of Visual Studio, and cleans / rebuilds of the application.

Any ideas? (These are for the items in a ListBox, so x:Key is not an option.)

P.S. How do I get rid of all those trailing blank lines in my code listing?

DETAILS:

MyClasses.cs

namespace MyNamespace {
  internal class MyClassInternal {}
  public class MyClassPublic {}
}

MyUserControl.xaml

<UserControl x:Class="MyNamespace.MyUserControl"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="clr-namespace:MyNamespace"         
    Height="300" Width="300">

    <UserControl.Resources>
        <DataTemplate DataType="{x:Type local:MyClassInternal}"/> <!--OK-->

        <ObjectDataProvider x:Key="ClassPublicKey" ObjectType="{x:Type local:MyClassPublic}"/> <!--OK--> 

        <!-- Type reference cannot find public type named 'MyClassPublic' -->
       <DataTemplate DataType="{x:Type local:MyClassPublic}"/> <!--FAILS-->
    </UserControl.Resources>

    <TextBlock>Hello World</TextBlock>
</UserControl>

MyUserControl.xaml.cs

using System.Windows.Controls;

namespace MyNamespace {
    public partial class MyUserControl :UserControl {
        public MyUserControl() {
            InitializeComponent();
        }
    }
}

Answer 1

It was caused by having a space in the Assembly name.