ColumnSpan example
<UserControl x:Class='SilverlightApplication3.MainPage' xmlns='http://schemas.microsoft.com/winfx/2006/xaml/presentation' xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml' xmlns:d='http://schemas.microsoft.com/expression/blend/2008' xmlns:mc='http://schemas.openxmlformats.org/markup-compatibility/2006' mc:Ignorable='d' d:DesignWidth='640' d:DesignHeight='480'> <Canvas> <Grid> <Grid.RowDefinitions> <RowDefinition/> <RowDefinition/> </Grid.RowDefinitions> <Grid.ColumnDefinitions> <ColumnDefinition/> <ColumnDefinition/> </Grid.ColumnDefinitions> <Button Grid.Row="0" Grid.Column="0" Grid.ColumnSpan="2" Content="Button 1" /> <Button Grid.Row="1" Grid.Column="0" Content="Button 2"/> <Button Grid.Row="1" Grid.Column="1" Content="Button 3"/> </Grid> </Canvas> </UserControl>