WPF

        //  http://www.beacosta.com/blog/?p=41
        private T GetObjectOfTypeInVisualTree<T>(DependencyObject dpob) where T : DependencyObject
        {
            int count = VisualTreeHelper.GetChildrenCount(dpob);
            for (int i = 0; i < count; i++)
            {
                DependencyObject child = VisualTreeHelper.GetChild(dpob, i);
                T childAsT = child as T;
                if (childAsT != null)
                {
                    return childAsT;
                }
                childAsT = GetObjectOfTypeInVisualTree<T>(child);
                if (childAsT != null)
                {
                    return childAsT;
                }
            }
            return null;
        }

        private void ManualStartAnimation(string templateName, string elementName, RoutedEventArgs eventArgs)
        {
            //  this works too
            //  http://social.msdn.microsoft.com/Forums/en-US/wpf/thread/4a04938b-690b-4bd0-969a-6dc4f6d6fda5/

            //  this is implemented
            //  http://joshsmithonwpf.wordpress.com/2007/06/28/how-to-use-findname-with-a-contentcontrol/
            //  together with this (GetObjectOfTypeInVisualTree)
            //  http://www.beacosta.com/blog/?p=41

            DataTemplate   _dt = (DataTemplate)this.FindResource(templateName);
            if (_dt != null)
            {
               //  reminder: displayContent is the ContentControl
                ContentPresenter _cp = GetObjectOfTypeInVisualTree<ContentPresenter>(this.displayContent);
                if (_cp != null)
                {
                    UIElement _element = (UIElement)_dt.FindName(elementName, _cp);
                    if (_element != null)
                    {
                        _element.RaiseEvent(eventArgs);
                    }
                }
            }
        }

        public void ShowLogin()
        {
->kick     ManualStartAnimation("flipItemTemplate", "frontHost", new RoutedEventArgs(FlipToLoginEvent));
        }

Gideon Engelberth wrote:

You could try moving the trigger to the ComboBox level.

<ControlTemplate TargetType="{x:Type ComboBox}">
   <Grid>
      <Border Background="Green" x:Name="ComboBoxBorder">
         <Grid>
            <ToggleButton ... />
            <TextBox Visibility="Hidden" x:Name="PART_EditableTextBox" ...>
         </Grid>
      </Border>
   <Grid>
   <!-- other stuff here -->
   <ControlTemplate.Triggers>
      <!-- your trigger goes HERE -->
      <Trigger SourceName="PART_EditableTextBox" Property="UIElement.IsKeyboardFocused" Value="True">
         <Setter TargetName="ComboBoxBorder" Property="Background" Value="Blue" />
      </Trigger>
   </ControlTemplate.Triggers>
</ControlTemplate>

private _host = null;

private void StartServer()
{
  _host = new ServiceHost(typeof(DataBase.DataBaseService ), new Uri("http://localhost:8000/DataBaseService"));
  _host.AddServiceEndpoint(typeof(DataBase.IDataBaseService),
    new BasicHttpBinding(), "DataBaseService");
  _host.Open();
}

private void StopServer()
{
  if (_host != null)
  {
    _host.Close();
    _host.Dispose();
  }
}