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<Window x:Class="WpfApplication1.Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="Window1" Height="300" Width="300">
    <Window.Resources>
        <x:ArrayExtension Type="UIElement" x:Key="Collection">
            <TextBlock>Hello</TextBlock>
            <TextBox>World</TextBox>
        </x:ArrayExtension>
    </Window.Resources>
</Window>					

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  public partial class Window1 : Window
  {
    int index;
    UIElement[] collection;
    DispatcherTimer timer = new DispatcherTimer {
      Interval = TimeSpan.FromSeconds(1)
    };

    public Window1()
    {
      InitializeComponent();
      collection = (UIElement[])Resources["Collection"];
      timer.Tick += delegate
      {
        Content = collection[index++ % 2];
      };
      timer.Start();
    }
  }					

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<TabControl.Template>
            <ControlTemplate TargetType="TabControl">
                <ContentPresenter x:Name="PART_SelectedContentHost"
                                  ContentSource="SelectedContent" />
            </ControlTemplate>
        </TabControl.Template>