Change ToggleButton Background in WPF

Question

I'm changing the background of a ToggleButton on MouseOver like this :

    <Style x:Key="ToggleButtonStyle" TargetType="{x:Type ToggleButton}">
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type ToggleButton}">
                    <Border  x:Name="border" 
                             Background="{TemplateBinding Background}"                                                                 
                        <ControlTemplate.Triggers>
                        <Trigger Property="IsMouseOver" Value="true">
                            <Setter 
                                TargetName="border"
                                Property="Background"
                                Value="{StaticResource ToggleButtonMouseHover}"/>                                
                        </Trigger>
                    </ControlTemplate.Triggers>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style> 

I don't understand why we have to use a Border control. Do you have an explanation?

Thanks.

Answer 1

Thanks to everyone, the point is that a background needs a container.