<Window x:Class="Workspace.DockExample"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="Workspace" Width="640" Height="480">
<Rectangle Width="50" Height="50" Grid.Row="2" Grid.Column="1">
<Rectangle.Fill>
<VisualBrush>
<VisualBrush.Visual>
<StackPanel Background="White">
<Button Margin="1">A Button</Button>
<Button Margin="1">Another Button</Button>
</StackPanel>
</VisualBrush.Visual>
</VisualBrush>
</Rectangle.Fill>
</Rectangle>
</Window>
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