Change circle button background image on click in WPF

Question

I have a circle button below

<Button  x:Name="btnLight" Width="72" Height="72" Content="" Margin="180,0,372,94" VerticalAlignment="Bottom" d:LayoutOverrides="VerticalAlignment">
            <Button.Template>
                <ControlTemplate>
                    <Grid>
                        <Ellipse>
                            <Ellipse.Fill>
                                <ImageBrush ImageSource="Images/light-off.jpg"/>
                            </Ellipse.Fill>
                        </Ellipse>
                    </Grid>
                </ControlTemplate>
            </Button.Template>
    </Button>

How do I change the background image (Images/light-on.jpg) when I click it? Thank you!

Answer 1

Wow! You have been given some complicated answers here... you're all doing too much work!!! This question has a really simple solution. First, let's sort out this ControlTemplate the way it should be:

<Button x:Name="btnLight" Width="72" Height="72" Content="" Margin="180,0,372,94" 
    VerticalAlignment="Bottom">
    <Button.Template>
        <ControlTemplate>
            <Ellipse Name="Ellipse" Fill="{TemplateBinding Background}" />
        </ControlTemplate>
    </Button.Template>
</Button>

Now, you can add a really simple Style to perform your image change:

<Style TargetType="{x:Type Button}">
    <Setter Property="Button.Background">
        <Setter.Value>
            <ImageBrush ImageSource="Images/Add_16.png" />
        </Setter.Value>
    </Setter>
    <Style.Triggers>
        <Trigger Property="Button.IsPressed" Value="True">
            <Setter Property="Button.Background">
                <Setter.Value>
                    <ImageBrush ImageSource="Images/Copy_16.png" />
                </Setter.Value>
            </Setter>
        </Trigger>
    </Style.Triggers>
</Style>