Extending a Style using the BasedOn attribute
<Page xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"> <Page.Resources> <Style x:Key="MyStyle"> <Setter Property="Control.Width" Value="200" /> </Style> <Style x:Key="MyStyle2" BasedOn="{StaticResource MyStyle}"> <Setter Property="Control.Width" Value="300"/> <Setter Property="Control.FontWeight" Value="Bold" /> <Setter Property="Control.Height" Value="50" /> </Style> </Page.Resources> <StackPanel> <Button Style="{StaticResource MyStyle}" Content="A"/> <Button Style="{StaticResource MyStyle2}" Content="B"/> </StackPanel> </Page>