如何在wpf/xaml中使用触发器获得按钮上的圆角

<Button Content="按钮" Style="{StaticResource CustomButtonStyle}" />

<Window.Resources>
    <Style x:Key="CustomButtonStyle" TargetType="Button">
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="Button">
                    <Border x:Name="border" Background="LightGray" BorderBrush="DarkGray" BorderThickness="1" CornerRadius="0">
                        <ContentPresenter HorizontalAlignment="Center" VerticalAlignment="Center" />
                    </Border>
                    <ControlTemplate.Triggers>
                        <Trigger Property="IsMouseOver" Value="True">
                            <Setter TargetName="border" Property="Background" Value="Gray" />
                        </Trigger>
                        <Trigger Property="IsPressed" Value="True">
                            <Setter TargetName="border" Property="Background" Value="DarkGray" />
                        </Trigger>
                    </ControlTemplate.Triggers>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>
</Window.Resources>