How to create a DocumentGroup with two tabs

This example shows how to create a DocumentGroup with two tabs, represented by DocumentPanel objects.

<dxdo:DocumentGroup x:Name="documentGroup1" ItemHeight="2*" SelectedTabIndex="1">
    <dxdo:DocumentPanel x:Name="document1" Caption="Document 1">
        <RichTextBox />
    </dxdo:DocumentPanel>
    <dxdo:DocumentPanel x:Name="document2" Caption="Document 2">
        <RichTextBox />
    </dxdo:DocumentPanel>
</dxdo:DocumentGroup>