Template Binding to background and foreground colors?

Question

I'm building a simple ControlTemplate for a Button. I want to draw a 2 color gradient, and bind the two colors so I don't need to hard code them in the template. But since Background and Foreground are Brushes and not just Colors, I'm not sure this will work.

Can anyone tell me if there is a good way to do this? it seems simple enough. Thanks.

<ControlTemplate x:Key="ElipseButton" TargetType="Button">
  <Ellipse>
   <Ellipse.Fill>
    <RadialGradientBrush RadiusX="1" RadiusY="1" GradientOrigin="0.7,0.8">
              <GradientStop Color="White" Offset="0"/>
     <GradientStop Color="Black" Offset="1"/>
    </RadialGradientBrush>
   </Ellipse.Fill>
  </Ellipse>
 </ControlTemplate>

I want to replace the 'Black' and 'White' colors with TemplateBindings.

Answer 1

Personally, I would just put the entire Brush into your template. This gives you much more control, later, as it allows you to change (via template changes) the brush from a radial gradient to a linear gradient, etc.

Answer 2

You can use attached properties to add some new Color properties that you can use on Button:

public class ColorExtensions
{
    public static readonly DependencyProperty ColorFrontProperty = DependencyProperty.RegisterAttached(
        "ColorFront",
        typeof(Color),
        typeof(ColorExtensions),
        new UIPropertyMetadata(Colors.White));

    public static Color GetColorFront(DependencyObject target)
    {
        return (Color)target.GetValue(ColorFrontProperty);
    }

    public static void SetColorFront(DependencyObject target, Color value)
    {
        target.SetValue(ColorFrontProperty, value);
    }

    public static readonly DependencyProperty ColorBackProperty = DependencyProperty.RegisterAttached(
        "ColorBack",
        typeof(Color),
        typeof(ColorExtensions),
        new UIPropertyMetadata(Colors.Black));

    public static Color GetColorBack(DependencyObject target)
    {
        return (Color)target.GetValue(ColorBackProperty);
    }

    public static void SetColorBack(DependencyObject target, Color value)
    {
        target.SetValue(ColorBackProperty, value);
    }
}

You can then set these on any instance and access them in your template using normal Bindings (TemplateBindings won't work here):

<Button Content="Click Me" local:ColorExtensions.ColorFront="Red">
    <Button.Template>
        <ControlTemplate TargetType="Button">
            <Ellipse>
                <Ellipse.Fill>
                    <RadialGradientBrush RadiusX="1" RadiusY="1" GradientOrigin="0.7,0.8">
                        <GradientStop Color="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=(local:ColorExtensions.ColorFront)}" Offset="0"/>
                        <GradientStop Color="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=(local:ColorExtensions.ColorBack)}" Offset="1"/>
                    </RadialGradientBrush>
                </Ellipse.Fill>
            </Ellipse>
        </ControlTemplate>
    </Button.Template>
</Button>