title: How to control "update trigger" in oneway databinding in wpf?
body: <p>When using databinding in WPF, if you set <code>Mode</code> property to <code>TwoWay</code>, you can control the moment when the source property will be updated by setting <code>UpdateSourceTrigger</code> property. That scenario is possible for target -> source update stream. But how you can control same thing for source -> target update stream? I cannot find equivalent property.</p>
  
  <p>For example, lets say I have two textboxes on my window, and I want to bind Text properties of both textboxes. XAML may look like this:</p>
  
  <pre><code>        &lt;TextBox
              Name="txt1"
              Text="{Binding ElementName=txt2, Path=Text, Mode=TwoWay,
              UpdateSourceTrigger=LostFocus}"
              /&gt;
          &lt;TextBox
              Name="txt2"
              /&gt;
  </code></pre>
  
  <p>When user enters text in <code>txt1</code> TextBox, <code>Text</code> property of <code>txt2</code> Textbox will be updated as <code>Text</code> property changes, just if I had implemented TextChanged event on <code>txt1</code>.</p>
  
  <p>However, when user enters text in <code>txt2</code> TextBox, <code>Text</code> property of <code>txt1</code> Textbox will be updated after <code>txt2</code> TextBox looses focus because <code>UpdateSourceTrigger</code> property is set to <code>LostFocus</code>, just if I had implemented LostFocus event.</p>
  
  <p>Is there possibility in WPF databinding to update target property after source property control looses focus? In our example: what should be done to XAML code above, so <code>Text</code> property of <code>txt2</code> TextBox would be updated only after <code>txt1</code> TextBox loose focus, and not after its Text property changes?</p>
  
  <p>Thanks!</p>