title: DesignInstance not working in VS2012
body: <p>I just spent several hours on an issue when using VS2012, WPF 4.5 and design-time data, specifically the DesignInstance attribute.</p>
  
  <p><strong>Goal</strong>: I wanted to have design-time data support in my WPF project (MVVM-based), both in VS2012 and Blend, and I could not for the life of me make the MVVMLight approach work <em>consistently</em>. </p>
  
  <p>So I tried to change to "just" using the built-in support for design-time data, using the markup extension provided with Blend.</p>
  
  <p><strong>Problem</strong>: Consider the following code:</p>
  
  <pre><code>&lt;Window x:Class="Nova.View.AlertsView"
          xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
          xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
          xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
          xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
          xmlns:local="clr-namespace:Nova.View"
          xmlns:vm="clr-namespace:Nova.ViewModel"
          mc:Ignorable="d"
          DataContext="{Binding Alerts, Source={StaticResource Locator}}" 
          d:DataContext="{d:DesignInstance vm:DesignAlertsViewModel, IsDesignTimeCreatable=True}"
  ... /&gt;
  </code></pre>
  
  <p>Both VS2012 and Blend reports "the name DesignAlertsViewModel does not exist in the namespace clr-namespace:Nova.ViewModel", even though intellisense resolves it just fine, and you have checked a thousand times that the namespace and class name are both correct.</p>