title: WPF TextBox with validation loses ErrorTemplate
body: <p>I have an issue very similar to these:</p>
  
  <p><a href="https://stackoverflow.com/questions/2355661/issue-with-wpf-validationidataerrorinfo-and-tab-focusing">Issue with WPF validation(IDataErrorInfo) and tab focusing</a></p>
  
  <p><a href="https://stackoverflow.com/questions/9907075/textbox-with-validation-loses-errortemplate-on-tab-change">TextBox with validation loses ErrorTemplate on tab change</a></p>
  
  <p><code>AdornerDecorator</code> do the trick <strong>within the same instance</strong> of the <code>Window</code>, but when the <code>Window</code> is reloaded and I switch to the <code>TabItem</code> containing the <code>TextBox</code> in error, the <code>ErrorTemplate</code> <em>won't show up anymore</em>.</p>
  
  <pre class="lang-xml prettyprint-override"><code>&lt;Window x:Class="Views.MyWindowView"&gt;
      &lt;Grid&gt;
  
          &lt;Grid.RowDefinitions&gt;
              &lt;RowDefinition Height="*"/&gt;
              &lt;RowDefinition Height="Auto"/&gt;
          &lt;/Grid.RowDefinitions&gt;
  
          &lt;TabControl HorizontalAlignment="Stretch" 
                      Height="Auto"
                      VerticalAlignment="Top"
                      Width="Auto"
                      SelectionChanged="TabItemChanged"
                      Name="MyTabControl"&gt;
  
              &lt;!-- Below, AdornerDecorator are added for the following reason:
                   the Validation.Error cues are painted in the Adorner Layer. 
                   When tabs are switched, that layer is discarded. --&gt;
  
              &lt;!-- The view 1 tab.--&gt;
              &lt;TabItem Header="{Resx tab1_Header}"
                       Name="Tbi1"&gt;
                  &lt;AdornerDecorator&gt;
                      &lt;vw:MyView1 DataContext="{Binding}"/&gt;
                  &lt;/AdornerDecorator&gt;
              &lt;/TabItem&gt;
  
              &lt;!-- The view 2 tab.--&gt;
              &lt;TabItem Header="{Resx tab2_Header}"
                       Name="Tbi2"&gt;
                  &lt;AdornerDecorator&gt;
                      &lt;vw:MyView2 DataContext="{Binding}"/&gt;
                  &lt;/AdornerDecorator&gt;
              &lt;/TabItem&gt;
          &lt;/TabControl&gt;
  </code></pre>
  
  <p>...</p>
  
  <p>I tried to retrigger the validation in the code-behind on <code>TabControl</code> <code>SelectionChanged</code>, didn't work. </p>
  
  <p>Any idea?</p>