title: XAML:The attachable property VisualStateGroups was not found in type VisualStateManager
body: <p>I'm using VS2008 EE SP1 + WPF + XAML.
  In the beginning I added a reference to it:</p>
  
  <pre><code>xmlns:vsm="clr-namespace:System.Windows;assembly=System.Windows"
  </code></pre>
  
  <p>I'm getting this error  while compilation:</p>
  
  <pre><code>&lt;vsm:VisualStateManager.VisualStateGroups&gt;  
     &lt;vsm:VisualStateGroup x:Name="CommonStates"&gt;
                          &lt;vsm:VisualStateGroup.Transitions&gt;
                              &lt;vsm:VisualTransition To="MouseOver" Duration="0:0:0.1"/&gt;
                              &lt;vsm:VisualTransition To="Pressed" Duration="0:0:0.1"/&gt;
                          &lt;/vsm:VisualStateGroup.Transitions&gt;
                          &lt;vsm:VisualState x:Name="Normal"/&gt;
                          &lt;vsm:VisualState x:Name="MouseOver"&gt;
                              &lt;Storyboard&gt;
                                  &lt;DoubleAnimation Duration="0:0:0.1" Storyboard.TargetName="Highlight" Storyboard.TargetProperty="Opacity" To="1"/&gt;
                              &lt;/Storyboard&gt;
  </code></pre>
  
  <p>Does anybody know the reason and possible workaround?</p>