Margin vs Padding and Grid
<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'> <Grid ShowGridLines="True" Background="Cyan"> <Grid.ColumnDefinitions> <ColumnDefinition Width="Auto" /> <ColumnDefinition Width="Auto" /> <ColumnDefinition Width="Auto" /> </Grid.ColumnDefinitions> <Grid.RowDefinitions> <RowDefinition Height="Auto" /> </Grid.RowDefinitions> <Button Grid.Column="0" Margin="20" Padding="0" >Click me!</Button> <Button Grid.Column="1" Margin="10" Padding="10">Click me!</Button> <Button Grid.Column="2" Margin="0" Padding="20">Click me!</Button> </Grid> </UserControl>