Trigger won't change Background

Question

I\'m trying to create a template for buttons in order to prevent the graying of the control when it is disabled, it is working just fine, but for some reason it won\'t chang

Answer 1

It wont change the color because you "overlay" the color with the color you defined in MainWindow.xaml.

Its called dependency property value precedence.

To read more about it take a look at this:

http://msdn.microsoft.com/en-us/library/ms743230.aspx

What happens in your case is that you defined a background in style and in trigger but then you set the value in MainWindow. The value set in MainWindow is considered the local value and the ones set in style are "style - values".

If you take a look at the link I gave you you will see that local value comes first before "style - values".

Local values are very powerful.

That is why your Button will always be Orange even when disabled. The property system will try to find a value for the background when your trigger fires and it will always find the local one because that is the value with the highest prority.

In order to make this work properly you will have to use SetCurrentValue instead of SetValue when setting the value of Button's background. (Means you will have to override Buttons code)

Take a look at this:

http://msdn.microsoft.com/en-us/library/system.windows.dependencyobject.setcurrentvalue.aspx

This method is used by a component that programmatically sets the value of one of its own properties without disabling an application's declared use of the property. The SetCurrentValue method changes the effective value of the property, but existing triggers, data bindings, and styles will continue to work.

Edit:

Example to understand dependency property value precedence and hit testing.

<Window.Resources>
    <Style TargetType="{x:Type Grid}">
        <Style.Triggers>
            <Trigger Property="IsMouseOver" Value="True">
                <Setter Property="Background" Value="Yellow" />
            </Trigger>
        </Style.Triggers>
    </Style>
    <Style TargetType="{x:Type TextBlock}">
        <Style.Triggers>
            <Trigger Property="IsMouseOver" Value="True">
                <Setter Property="Background" Value="Red" />
            </Trigger>
        </Style.Triggers>
    </Style>
</Window.Resources>
<Grid>
    <TextBlock Height="20" Margin="40" Text="asdfasdfa" VerticalAlignment="Bottom"/>
    <Rectangle  Height="100" VerticalAlignment="Bottom" >
        <Rectangle.Fill>
            <LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
                <GradientStop Offset="0"/>
                <GradientStop Color="White" Offset="1"/>
            </LinearGradientBrush>
        </Rectangle.Fill>
    </Rectangle>
</Grid>

Answer 2

Just a note: the Background property is of type Brush, so you should write

<Border Background="{TemplateBinding Background}" ...>
    ...
</Border>

instead of

<Border ...>
    <Border.Background>
        <SolidColorBrush Color="{TemplateBinding Background}" />
    </Border.Background>
    ...
</Border>

Answer 3

If you look at DependecyProperty value precedence order you will see that setting a value explicitly (treated as local value) on a control will override any values set by the trigger.