title: IsSelected property of WPF TabItem
body: <p>I have the following code:</p>
  
  <pre><code>&lt;TabItem Name="tabItemGeneral"&gt;
      &lt;TabItem.Triggers&gt;
          &lt;Trigger Property="IsSelected" Value="True"&gt;
              &lt;Setter TargetName="tabGeneralImg" Property="Source" Value="Image/tabGeneralActive.png"&gt;&lt;/Setter&gt;
          &lt;/Trigger&gt;
      &lt;/TabItem.Triggers&gt;
      &lt;TabItem.Header&gt;
          &lt;StackPanel Orientation="Horizontal" Margin="0,-3,0,0"&gt;
              &lt;Image Name="tabGeneralImg" Source="Images/tabGeneral.png" Width="11" Height="11"&gt;&lt;/Image&gt;
              &lt;Label Name="tabGeneralLbl" Content="General"&gt;&lt;/Label&gt;
          &lt;/StackPanel&gt;
      &lt;/TabItem.Header&gt;
      &lt;Grid&gt;
          &lt;!-- ... --&gt;
      &lt;/Grid&gt;
  &lt;/TabItem&gt;
  </code></pre>
  
  <p>but I get 
  Error   1   'IsSelected' member is not valid because it does not have a qualifying type name.   C:\MyNET\bluetooth\iLockWPF\iLock\iLock\MainWindow.xaml 63  60  iLock</p>
  
  <p>during compilation. Why?</p>