WPF window style not being applied

Question

I have a ResourceDictionary that contains Style definitions for controls used within my application.

All of the styles are applied properly to the controls in the window...but the style in the ResourceDictionary for the window itself is not being applied.

This is the XAML in my ResourceDictionary that contains the style that I want to apply to my window:

<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                    xmlns:primatives="clr-namespace:System.Windows.Controls.Primitives;assembly=PresentationFramework"
                    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
    <Style TargetType="{x:Type Window}">
        <Setter Property="Background" Value="#FF121212"></Setter>
        <Setter Property="Height" Value="768"></Setter>
        <Setter Property="Width" Value="1024"></Setter>
    </Style>
<!-- .... -->
</ResourceDictionary>

This is the XAML for the window that I am working with (trying to get this style to apply):

<Window x:Class="TryingStyles"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="TryingStyles">
    <Window.Resources>
        <ResourceDictionary>
            <ResourceDictionary.MergedDictionaries>
                <ResourceDictionary Source="Resources/StylesDictionary.xaml" />
            </ResourceDictionary.MergedDictionaries>
        </ResourceDictionary>
    </Window.Resources>    
    <StackPanel>
        <StackPanel Orientation="Horizontal">
            <Label Content="Label" Height="28" HorizontalAlignment="Left" Margin="12,12,0,0" Name="Label1" VerticalAlignment="Top" />
            <TextBox Height="23" HorizontalAlignment="Left" Margin="56,14,0,0" Name="TextBox1" VerticalAlignment="Top" Width="120" />
        </StackPanel>
        <StackPanel Orientation="Horizontal">
            <TabControl Height="206" HorizontalAlignment="Left" Margin="12,43,0,0" Name="TabControl1" VerticalAlignment="Top" Width="250">
                <TabItem Header="TabItem1" Name="TabItem1">
                    <Grid></Grid>
                </TabItem>
            </TabControl>
            <GroupBox Header="GroupBox1" Margin="268,43,12,12" Width="396"></GroupBox>
        </StackPanel>
    </StackPanel>
</Window>

It appears that the style for the window is applied when I view the window in the IDE's "Design view" but when I run the application the style is not applied.

Does anyone know what I'm doing wrong?

Answer 1

It appears that there is no proper solution to your problem. TargetType in Styles doesn't manage derived types. Here are two alternatives : You can put a key in your style and apply the style to all your Windows.

    <!-- Resource file -->    
    <ResourceDictionary ...>
        <Style TargetType="{x:Type Window}" x:Key="WindowDefaultStyle">
            <!-- .... -->    
        </Style>
    </ResourceDictionary>

    <!-- Window file -->
    <Window Style="{DynamicResource ResourceKey=WindowDefaultStyle}">

Or you can use the BasedOn property of the Style.

<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                    xmlns:my="clr-namespace:WpfApplication1">
    <Style TargetType="{x:Type Window}" x:Key="BaseStyle">
        <Setter Property="Background" Value="#FF121212"></Setter>
        <Setter Property="Height" Value="768"></Setter>
        <Setter Property="Width" Value="1024"></Setter>
    </Style>

    <!-- Inherit from the BaseStyle and define for the MainWindow class -->
    <Style TargetType="{x:Type my:MainWindow}" BasedOn="{StaticResource ResourceKey=BaseStyle}" />
</ResourceDictionary>

Answer 2

It's very strange that it works with the designer but not when the application runs. The problem seems to be the TargetType of your Style. Wpf seems not be able to match the Window class with your derivated class TryingStyles.

Change your TargetType and it will work :

<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                    xmlns:primatives="clr-namespace:System.Windows.Controls.Primitives;assembly=PresentationFramework"
                    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                    xmlns:my="clr-namespace:WpfApplication1">
    <Style TargetType="{x:Type my:TryingStyles}">
        <Setter Property="Background" Value="#FF121212"></Setter>
        <Setter Property="Height" Value="768"></Setter>
        <Setter Property="Width" Value="1024"></Setter>
    </Style>
    <!-- .... -->
</ResourceDictionary>