title: Ext.Net RadioGroup CheckedItems is always null
body: <p>I'm seeing strange behaviour from Ext.Net 2.0: RadioGroup.CheckedItems is always zero in my change handler callback. In my code below RadioGroup1.CheckedItems is ALWAYS zero after checking. What am I doing wrong / how can I solve this?</p>
  
  <pre><code>[DirectMethod]
  public void TxtVisibility()
  {
      foreach (var item in RadioGroup1.CheckedItems)
      {
          if (item.ID == "rdHourly")
          {
              txtPerHour.Hidden = false;
              txtAtTime.Hidden = true;
          }
          else if (item.ID == "rdAtHourly")
          {
              txtPerHour.Hidden = true;
              txtAtTime.Hidden = false;
          }
      }  
  }
  </code></pre>
  
  <p>My calling code:</p>
  
  <pre><code>&lt;ext:RadioGroup ID="RadioGroup1" 
                  runat="server" 
                  FieldLabel="" 
                  ColumnsNumber="1"&gt;
      &lt;Items&gt;
          &lt;ext:Radio ID="rdHourly" FieldLabel="IsEveryPerHour"
                     Name="IsEveryPerHour" runat="server"
                     BoxLabel="Per Hour(s)" Padding="10"&gt;
          &lt;/ext:Radio&gt;
          &lt;ext:Radio ID="rdAtHourly" FieldLabel="IsAtHour"
                     Name="IsAtHour" runat="server"
                     BoxLabel="At" Padding="10"&gt;
         &lt;/ext:Radio&gt;
      &lt;/Items&gt;
      &lt;Listeners&gt;
           &lt;Change Handler="App.direct.TxtVisibility();" &gt;&lt;/Change&gt;
      &lt;/Listeners&gt;
  &lt;/ext:RadioGroup&gt; 
  </code></pre>