title: FindName does not work
body: <p>My <code>FindName</code> does not work, the value is null.<br>
  And I can't call my <code>x:Name="QuantiteTextBox"</code> in my code-behind...<br>
  The name seems to not exist in this context..</p>
  
  <p>XAML :  </p>
  
  <pre><code>&lt;GridViewColumn Width="Auto" Header="Nb"&gt;
       &lt;GridViewColumn.CellTemplate&gt;
            &lt;DataTemplate&gt;
                 &lt;TextBox x:Name="QuantiteTextBox" Text="{Binding Quantite, ElementName=EditTableUserControl}" HorizontalAlignment="Center" Margin="-10,0,0,0"/&gt;
            &lt;/DataTemplate&gt;
       &lt;/GridViewColumn.CellTemplate&gt;
  &lt;/GridViewColumn&gt;
  </code></pre>
  
  <p>WPF :  </p>
  
  <pre><code>var quantiteTextBox = (TextBox)FindName("QuantiteTextBox");
  </code></pre>
  
  <p>How can I resolve this problem please ? Thanks.</p>