title: WPF TextBox Validation
body: <p>I have validation hooked up to a model that is bound to the <code>TextBox</code> container.  When the window is first opened validation errors appear as the model is empty, I do not want to see validation errors until submit of the window or the text in the <code>TextBox</code> has changed or on lost focus.</p>
  
  <p>Here is the <code>TextBox</code>:</p>
  
  <pre><code>&lt;TextBox Text="{Binding 
                     Path=Firstname, 
                     UpdateSourceTrigger=PropertyChanged, 
                     ValidatesOnDataErrors=True}"
           Width="124"
           Height="24"/&gt;
  </code></pre>
  
  <p>How can this be achieved?  </p>