title: wpf validation rules problem with textbox
body: <p>I created a class IntegersValidationRule which inherits from ValidationRule. Now I don't know what code should I write in XAML. That's what I have: <br></p>
  
  <pre><code>&lt;TextBox Name="defaultTxt"
       Height="23" Width="200"&gt;
    &lt;TextBox.Text&gt;
      &lt;Binding UpdateSourceTrigger="PropertyChanged"&gt;
        &lt;Binding.ValidationRules&gt;
          &lt;what:IntegersValidationRule/&gt;
        &lt;/Binding.ValidationRules&gt;
      &lt;/Binding&gt;
    &lt;/TextBox.Text&gt;
  &lt;/TextBox&gt;
  </code></pre>
  
  <p>I know that either I'm so stupid that I can't understand in many tutorials what Path in Binding property means, why should we use Binding here when there's no binding required and what should I use instead of 'what' word inside Binding.ValidationRule.</p>