title: Changing (Enable/Disable) GroupStyle in ListView for different category items
body: <p>How can I switch between <code>GroupStyles</code> for a <code>ListView</code> based on some conditions at run time?  For instance I need to use Default for items that that have <code>GroupStyle</code> Header name null, and if it is not null then use the custom <code>GroupStyle</code> theme?  I tried <code>GroupStyleSelector</code>, and it doesn't work, because it works for multi level grouping, and in my case I have only one level grouping.</p>
  
  <p>If yes, then how?</p>
  
  <p>Custom <code>GroupStyle</code>:</p>
  
  <pre><code>    &lt;Style x:Key="grouping"
             TargetType="{x:Type GroupStyle}"&gt;
          &lt;Setter Property="ContainerStyle"&gt;
              &lt;Setter.Value&gt;
                  &lt;Style TargetType="{x:Type GroupItem}"&gt;
                      &lt;Setter Property="Margin"
                              Value="0,0,0,5" /&gt;
                      &lt;Setter Property="Template"&gt;
                          &lt;Setter.Value&gt;
                              &lt;ControlTemplate TargetType="{x:Type GroupItem}"&gt;
                                  &lt;Expander IsExpanded="False"
                                            BorderBrush="#FFA4B97F"
                                            BorderThickness="0,0,0,1"&gt;
                                      &lt;Expander.Header&gt;
                                          &lt;DockPanel&gt;
                                              &lt;TextBlock FontWeight="Bold"
                                                         Text="{Binding Name}"
                                                         Margin="0"
                                                         Width="250" /&gt;
                                              &lt;TextBlock FontWeight="Bold"
                                                         Text="{Binding Path=Items[0].StartTime, StringFormat=T}" /&gt;
                                          &lt;/DockPanel&gt;
                                      &lt;/Expander.Header&gt;
                                      &lt;Expander.Content&gt;
                                          &lt;ItemsPresenter /&gt;
                                      &lt;/Expander.Content&gt;
                                  &lt;/Expander&gt;
                              &lt;/ControlTemplate&gt;
                          &lt;/Setter.Value&gt;
                      &lt;/Setter&gt;
                  &lt;/Style&gt;
              &lt;/Setter.Value&gt;
          &lt;/Setter&gt;                    
      &lt;/Style&gt;
  </code></pre>
  
  <p>Thanks a lot.</p>
  
  <p>Sincerely,
  Vlad. </p>