Question

<Window x:Class="AiweeeTest.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525">
    <Grid>
        <Grid.Resources>
            <SolidColorBrush x:Key="backcolorType" Color="Red"></SolidColorBrush>
            <SolidColorBrush x:Key="forecolorType" Color="Green"></SolidColorBrush>
            <Style x:Key="TextboxStyle" TargetType="{x:Type TextBox}">
                <Setter Property="Background" Value="Yellow"/>
                <Style.Triggers>
                    <Trigger Property="IsEnabled" Value="false">
                        <Setter Property="Background" Value="{StaticResource backcolorType}"/>
                        <Setter Property="Foreground" Value="{StaticResource forecolorType}"/>
                    </Trigger>
                </Style.Triggers>
            </Style>
        </Grid.Resources>
        <TextBox Name="textbox1" Width="100" Height="25" Style="{StaticResource TextboxStyle}" IsEnabled="False"/>
    </Grid>
</Window>

I am not able to update the background of a textbox using the trigger defined above, however when I copy the entire textbox control template template and replace the “DisabledBackgroundBrush” with my own color it does. What’s the difference, I’ve already seen some links over this matter; however I am not able to understand the reason behind it. As I understand, Triggers are fired in the order they are defined, then the trigger defined locally in the window should be able to override the background color of the textbox when disabled. Please clarify.

PS: I am not trying to achieve anything special here, but just want to understand why is this so. This gives me a bit of frustration of WPF not being intuitive for situations like such.

Answer 1

I am guessing it has something to do with the order in which WPF will apply values for a DependencyProperty. This MSDN article has some good information on Dependency Property Precedence

Basically the order goes:

1. Property system coercion
2. Active animations, or animations with a Hold behavior.
3. Local value
4. TemplatedParent template properties
5. Triggers from the TemplatedParent template
6. Property sets (typically through XAML attributes) in the TemplatedParent template
7. Implicit style
8. Style triggers
9. Template triggers
10. Style setters
11. Default (theme) style
12. Active triggers in the theme style
13. Setters in the theme style
14. Inheritance
15. Default value from dependency property metadata