Cannot change Background color with triggers in XAML.

Question

Hello,

I have a little problem and I don't know how can I fix it ...

I created a CustomControl called "StandardKeyView" from a Button. This control has a dependency property "DownImage" which is used to define a Background Image to my control during the mouse over.

Here's the definition of the DownImage property :

public SolidColorBrush DownImage
    {
        get { return (SolidColorBrush)GetValue( DownImageProperty ); }
        set { SetValue( DownImageProperty, value ); }
    }
    public static readonly DependencyProperty DownImageProperty = 
DependencyProperty.Register( "DownImage", typeof( SolidColorBrush ), typeof( StandardKeyView ) );

Here's the definition of a new StandardKeyView :

<skv:StandardKeyView Background="White" DownImage="Black"/>

Here's the default control template of a StandardKeyView :

    <ControlTemplate TargetType="{x:Type skv:StandardKeyView}" x:Key="DefaultStandardKeyViewTemplate">
    <Button Width="{TemplateBinding Width}" Height="{TemplateBinding Height}" Background="{TemplateBinding Background}" x:Name="MainButton" />
    <ControlTemplate.Triggers>
        <Trigger Property="IsMouseOver" Value="True">
            <Setter TargetName="MainButton" Property="Background" Value="{TemplateBinding Property=DownImage}" />
        </Trigger>
    </ControlTemplate.Triggers>
</ControlTemplate>

I think it should work fine, but not really. I have a weird error : when I try to start the application, I have a XamlParseException who said

Unable to convert the value of attribute 'Value' as an object of type ''.

I think the type of DownImage is good, then why doesn't it work when it used in the trigger?

Answer 1

Try using instead:

Value="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=DownImage}"