title: Dependency Property is not updating my Usercontrol
body: <p>The line below works for the TextBox DP <strong>Text</strong>, where CellNo is a property of a class which derives from INotifyPropertychanged. So here when I change the CellNo the Text will be updated and When I change the CellNo the Text will be updated. This will work fine.</p>
  
  <pre><code>Text="{Binding Path = CellNo, Mode=TwoWay,  UpdateSourceTrigger=PropertyChanged}"
  </code></pre>
  
  <p>I have create a user control which contain only one TextBox. I have defined one DP name CellValue as below:</p>
  
  <pre><code>public string CellValue
      {
          get { return (string)GetValue(CellValueProperty); }
          set { SetValue(CellValueProperty, value); }
      }
  
      // Using a DependencyProperty as the backing store for LimitValue.  This enables animation, styling, binding, etc...
      public static readonly DependencyProperty CellValueProperty =
          DependencyProperty.Register("CellValue", typeof(string), typeof(control), new FrameworkPropertyMetadata
          {
              BindsTwoWayByDefault = true,
          });
  </code></pre>
  
  <p>Now when I use this user control in any dialog and do the same binding as above, the Target ( TextBox inside User control) is NOT updating.</p>
  
  <pre><code> &lt;local:control
          x:Name="control" 
          CellValue="{Binding Path = CellNo, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"&gt;
  </code></pre>
  
  <p>Also inside user control I have binded the Text Property of TextBox to CellValue DP.</p>
  
  <p><strong>Inside User control</strong></p>
  
  <pre><code>&lt;TextBox                 
          Text="{Binding Path = CellValue}"
          Name="textBox2" /&gt;
  </code></pre>
  
  <p>I want when the CellValue changes the TextBox Text should also be updated, but with the above appoach it remains blank.</p>