x:Null

<Window x:Class="WpfApplication1.MainWindow"        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"        Title="Null Sample" Height="300" Width="300">    <Window.Resources>        <Style x:Key="{x:Type Button}" TargetType="{x:Type Button}">            <Setter Property="Width" Value="60"/>            <Setter Property="Height" Value="36"/>            <Setter Property="Margin" Value="5"/>        </Style>    </Window.Resources>    <StackPanel>        <Button Content="OK"/>        <Button Content="OK"/>        <Button Content="OK"/>        <Button Content="OK" Style="{x:Null}"/>    </StackPanel></Window>