WPF Bind ControlTemplate's content to Property in Control?

Question

I want to bind Border.Background in my Button ControlTemplate to the Background Property of my button. Usually I would use a TemplateBinding:

  <Style TargetType="Button" x:Key="ColuredButton">
                <Setter Property="Background" Value="LightGreen"/>
                <Setter Property="Template">
                    <Setter.Value>
                        <ControlTemplate TargetType="Button">
                            <Border x:Name="Border" CornerRadius="2" BorderThickness="1" BorderBrush="Gray">
                               <Border.Background>
                                    <LinearGradientBrush StartPoint="0,0" EndPoint="0,1">
                                        <GradientStop Color="{TemplateBinding Foreground}"/>
                                        <GradientStop Color="{TemplateBinding Background}"/>
                                    </LinearGradientBrush>
                                </Border.Background>
                                    <ContentPresenter Margin="2" HorizontalAlignment="Center" VerticalAlignment="Center" RecognizesAccessKey="True" />
                            </Border> 
                        </ControlTemplate>
                    </Setter.Value>
                </Setter>
            </Style>

But I get the error: "Cannot set TemplateBinding if not in a Template".. But I am in a Template! (It works if I dont use LinearGradientBrush and bind the borders Backround Property directly to {TemplateBinding Background}....

Answer 1

As @Snowbear said, you should bind Color to Color and not Color to Brush. But in his solution, TemplateBinding with deep property Path such as Foreground.Color isnt allowed as part of the binding markup.

So use the following...

    <Border.Background>
      <LinearGradientBrush StartPoint="0,0" EndPoint="0,1">
         <GradientStop Color="{Binding Foreground.Color,
                               RelativeSource={RelativeSource TemplatedParent}}"
                       Offset="0.2"/>
         <GradientStop Color="{Binding Background.Color,
                               RelativeSource={RelativeSource TemplatedParent}}"
                       Offset="0.6"/>
      </LinearGradientBrush>
   </Border.Background>

And it should work.

Answer 2

I think you might have some other error here, but it is not reported well. GradientStop accepts a Color in its corresponding property while Background and Foreground properties of a Button are brushes, not colors. If you think that Background and Foreground will be SolidColorBrush you might try accessing their Color property in your binding, but I'm not sure whether it will work or not:

<GradientStop Color="{TemplateBinding Foreground.Color}"/>