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UWP: application wide TextBlock foreground crashes app when set from static resource

I went through a lot of similar questions on SO, in regards to setting the foreground of a TextBlock through a static resource, but for whatever reason my UWP application keeps crashing on me.
I am starting to believe this is a limitation of UWP? Also, no stacktrace is generated from this.
I am using Microsoft Visual Studio Community 2022 v.17.2.6
ThemeColors.xaml
<ResourceDictionary
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<SolidColorBrush x:Key="MyOffWhiteBrush" Color="#eeeeee" />
</ResourceDictionary>
TextBlockStyle.xaml
<ResourceDictionary
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<Style TargetType="TextBlock">
<Setter Property="Foreground" Value="{StaticResource MyOffWhiteBrush}" />
</Style>
</ResourceDictionary>
App.xaml
<Application
x:Class="TestTextBlock.App"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="using:TestTextBlock">
<Application.Resources>
<ResourceDictionary>
<ResourceDictionary.MergedDictionaries>
<ResourceDictionary Source="ThemeColors.xaml" />
<ResourceDictionary Source="TextBlockStyle.xaml" />
</ResourceDictionary.MergedDictionaries>
</ResourceDictionary>
</Application.Resources>
</Application>
MainPage.xaml
<Page
x:Class="TestTextBlock.MainPage"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="using:TestTextBlock"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d">
<Grid>
<TextBlock Text="helloworld" />
</Grid>
</Page>
UPDATE #1:
If I change TextBlockStyle.xaml to this it works.
<ResourceDictionary
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<SolidColorBrush x:Key="_" />
<Style TargetType="TextBlock">
<Setter Property="Foreground" Value="{StaticResource MyOffWhiteBrush}" />
</Style>
</ResourceDictionary>
I don't understand why I need to declare an empty brush?

The reason for this behavior may be related to the Lookup behavior for XAML resource references and Forward references within a ResourceDictionary. You need to make sure the referenced resource must appear lexically before the resource reference when you use the resource.
I agree with #Mark W, the possible workaround is that you could define the basic resource on top of other resources.
In your scenario, it should be like this:
<ResourceDictionary
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<ResourceDictionary.MergedDictionaries>
<ResourceDictionary Source="ThemeColors.xaml"/>
</ResourceDictionary.MergedDictionaries>
<Style TargetType="TextBlock">
<Setter Property="Foreground" Value="{StaticResource MyOffWhiteBrush}" />
</Style>

I don't have the answer for why... In my application, I have a number of styles - separated out into color/brushes, sizes and layouts, and then default styles... for each dictionary that references other dictionaries, I include them at the top.
ColorsAndBrushes does not have any references.
SizesAndLayout does not have any references.
DefaultStyles references the two above.
<ResourceDictionary.MergedDictionaries>
<ResourceDictionary Source="ColorsAndBrushes.xaml" />
<ResourceDictionary Source="SizesAndLayout.xaml" />
</ResourceDictionary.MergedDictionaries>
so for my next layer, "NamedStyles", I have have the following to the top:
<ResourceDictionary.MergedDictionaries>
<ResourceDictionary Source="ColorsAndBrushes.xaml" />
<ResourceDictionary Source="SizesAndLayout.xaml" />
<ResourceDictionary Source="DefaultStyles.xaml" />
</ResourceDictionary.MergedDictionaries>
I don't know if this will work better for you, but maybe feels a little better than the random empty brush. And my app.xaml references all of them. This was build on a older (AnniversaryEdition) UWP SDK, so your mileage may vary.
Good luck!
-Mark

Metro Styles in resource dictionary

I am trying to style my WPF application with Mahapps Metro. I have added the all the needed .xaml files in my MergedDictionary in the App.xaml. If I write the following in a view file,
<Button DockPanel.Dock="Left" VerticalAlignment="Top" Style="{DynamicResource SquareButtonStyle}"/>
it works, i.e., the button is styled in the SquareButtonStyle style. But if I instead add the following in my own resource dictionary,
<Style TargetType="Button">
<Setter Property="Style" Value="{DynamicResource SquareButtonStyle}"/>
</Style>
I get an error message,
Setting of the property
"System.Windows.ResourceDictionary.DeferrableContent" has caused an
exception.
(my transation of the German error message). So how can I style all buttons, e.g., with SquareButtonStyle without having to do that on each button individually?
EDIT: Here is my app.xaml (the last dictionary, ResourceDic.xaml, is my own one where the above code is):
<Application xmlns:local="clr-namespace:MGM8" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation">
<Application.Resources>
<ResourceDictionary>
<ResourceDictionary.MergedDictionaries>
<ResourceDictionary>
<local:MGM8_BootStrapper p7:Key="bootstrapper" xmlns:p7="http://schemas.microsoft.com/winfx/2006/xaml" />
</ResourceDictionary>
<ResourceDictionary Source="pack://application:,,,/MahApps.Metro;component/Styles/Controls.xaml" />
<ResourceDictionary Source="pack://application:,,,/MahApps.Metro;component/Styles/Fonts.xaml" />
<ResourceDictionary Source="pack://application:,,,/MahApps.Metro;component/Styles/Colors.xaml" />
<ResourceDictionary Source="pack://application:,,,/MahApps.Metro;component/Styles/Accents/Blue.xaml" />
<ResourceDictionary Source="pack://application:,,,/MahApps.Metro;component/Styles/Accents/BaseLight.xaml" />
<ResourceDictionary Source="ResourceDic.xaml" />
</ResourceDictionary.MergedDictionaries>
</ResourceDictionary>
</Application.Resources>

Style property can't be set inside Style of any element.
Just declare your style at root level(a root resource Dictionary or App.xmal resources). Just create the style with TargetType Button don't give any key to it. it will be applied to all the buttons in the app.
for ex:
<Style TargetType="Button" BasedOn="{StaticResource SquareButtonStyle}" >
<Setter Property="Height" Value="50"/>
<Setter Property="BorderThickness" Value="2,1" />
</Style>
So above is extending your SquareButtonStyle for your application for all buttons(only if defined at root level).
Update:
You have to use following in your own Resource Dictionary:
<ResourceDictionary.MergedDictionaries>
<ResourceDictionary Source="SquareButtonStyle dictionary"/>
</ResourceDictionary.MergedDictionaries>
Then only you can create a button style based on SquareButtonStyle in your ResourceDictionary.

Unable to resolve resources using separate files

I feel like this is a common sense and trivial, but i don't understand what i'm doing to begin with. I don't have any other resource I can use for help either. Sometimes i wonder if I'm even googling the question right.
I have some custom styles & templates I've made, but now the file is rather large and difficult to work with. I want to put each style or template in there own XAML files (sorta like headers/implementation files) so that a friend could work on one and then we add it to the project. (Such as Dictionary1.xaml ... ). I started a blank project to keep it simple.
Dictionary1.XAML
<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<ResourceDictionary x:Key="SomeKey">
<Color x:Key="detailMark">Black</Color>
<SolidColorBrush x:Key="detailMarkBrush" Color="{StaticResource ResourceKey=detailMark}" />
<Style x:Key="flatTextBox" TargetType="{x:Type TextBox}">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type TextBox}">
<Grid>
<Rectangle Stroke="{StaticResource ResourceKey=detailMarkBrush}" StrokeThickness="1"/>
<TextBox Margin="1" Text="{TemplateBinding Text}" BorderThickness="0"/>
</Grid>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</ResourceDictionary>
App.XAML
<Application x:Class="WpfApplication1.App"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:WpfApplication1"
StartupUri="MainWindow.xaml">
<Application.Resources>
<local:MainWindow x:Key="SomeKey"/>
</Application.Resources>
</Application>
And MainWindow.XAML
<Window x:Class="WpfApplication1.MainWindow"
xmlns:local="clr-namespace:WpfApplication1"
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>
<TextBox Style="{DynamicResource flatTextBox}"> <!-- doesn't autocomplete/work -->
</TextBox>
</Grid>
</Window>
Edit:
<TextBox Style="{Binding Mode=OneWay, Source={StaticResource SomeKey}}">
<!-- Throws System.Windows.Markup.XamlParseException -->
</TextBox>

As Alex mentioned, the right way to do this is using Merged Dictionaries.
Therefore, you should structure your project correctly, otherwise it will end up in a mess.
Keeping your "blank project", it should look like this:
YourProject
App.xaml (.cs)
MainWindow.xaml (.cs)
SomeOtherWindow.xaml (.cs)
Resources folder
Dictionary1.xaml
Dictionary2.xaml
...
Then you have to decide:
Do you want the resources to be available application wide?
Or do you want the resources to vary between certain windows / user controls?
If you want #1, you have to merge the dictionaries in the App.xaml file:
<Application x:Class=...
...>
<Application.Resources>
<ResourceDictionary>
<ResourceDictionary.MergedDictionaries>
<ResourceDictionary Source="Resources/Dictionary1.xaml"/>
<ResourceDictionary Source="Resources/Dictionary2.xaml"/>
</ResourceDictionary.MergedDictionaries>
</ResourceDictionary>
</Application.Resources>
</Application>
If you want #2, you have to merge the dictionaries in the specific window / user control file:
<Window x:Class=...
...>
<Window.Resources>
<ResourceDictionary>
<ResourceDictionary.MergedDictionaries>
<ResourceDictionary Source="Resources/Dictionary1.xaml"/>
<ResourceDictionary>
<!-- Window specific resources -->
</ResourceDictionary>
</ResourceDictionary.MergedDictionaries>
</ResourceDictionary>
</Window.Resources>
<!-- Content -->
</Window>

Organizing Xaml - Unable to apply StaticResource from different xaml file

I have a situation where the wpf application is not able to pickup StaticResource and instead fails with XamlParseException. But if I used a DynamicResource instead, the resource is found and no exception occurs.
I was trying to style and organize wpf resources as recommended at http://projekt202.com/blog/2010/xaml-organization/
I have 2 projects accordingly, a wpf control library that houses all resources and a main wpf project which uses those resources. Here is the structure of the 2 projects
Projects Structure
Wpf_Theme.ControlLibrary
--ResourceDictionaries
----BaseControlStyles
------ButtonStyle.xaml
------TextBoxStyle.xaml
----Brushes
------DefaultBlueTheme
----ResourceLibrary.xaml
Wpf_Theme.Main
--App.xaml
--MainWindow.xaml
Contents of xaml files
ButtonStyle.xaml
<Style TargetType="{x:Type Button}">
<Setter Property="Background" Value="{StaticResource ControlBackground}"/>
<Setter Property="BorderBrush" Value="{StaticResource BorderColor}"/>
...
</Style>
DefaultBlueTheme.xaml (Brushes)
<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<SolidColorBrush x:Key="PanelBackground" Color="#C8DCF0"/>
<SolidColorBrush x:Key="BorderColor" Color="#6A8FB5"/>
<SolidColorBrush x:Key="SelectedItemBackground" Color="Wheat"/>
<SolidColorBrush x:Key="TextForeground" Color="Black"/>
<LinearGradientBrush x:Key="ControlBackground" StartPoint="0,0" EndPoint="0,1">
<LinearGradientBrush.GradientStops>
<GradientStop Offset="0" Color="#DBECFD"/>
<GradientStop Offset="0.5" Color="#C7DBEF"/>
<GradientStop Offset="1" Color="#B0CAE5"/>
</LinearGradientBrush.GradientStops>
</LinearGradientBrush>
</ResourceDictionary>
ResourceLibrary.xaml (Merges all dictionaries in one file to be used by main project)
<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<ResourceDictionary.MergedDictionaries>
<ResourceDictionary Source="Brushes/DefaultBlueTheme.xaml"/>
<ResourceDictionary Source="BaseControlStyles/ButtonStyle.xaml"/>
</ResourceDictionary.MergedDictionaries>
</ResourceDictionary>
App.xaml (In Main project)
<Application x:Class="Wpf_Themes.Main.App"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
StartupUri="MainWindow.xaml">
<Application.Resources>
<ResourceDictionary>
<ResourceDictionary.MergedDictionaries>
<ResourceDictionary
Source="/Wpf_Themes.ControlLibrary;component/ResourceDictionaries/ResourceLibrary.xaml"/>
</ResourceDictionary.MergedDictionaries>
</ResourceDictionary>
</Application.Resources>
</Application>
MainWindow.xaml
<Window x:Class="Wpf_Themes.Main.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">
<StackPanel Width="200" Margin="10">
<Button>Click Me</Button>
</StackPanel>
</Window>
As stated earlier in the post, I am not able to resolve the style(Background and Border brushes) for the Button using the StaticResource applied in ButtonStyle.xaml. If I use DynamicResource instead, the brushes are found correctly and applied to the Button. Any insights why this behavior occurs.
Edit:
Following Mike's suggestion, I included the xaml files from the Wpf_Theme.ControlLibrary project directly into the App.xaml of the Main project like below
App.xaml
<Application x:Class="Wpf_Themes.Main.App"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
StartupUri="MainWindow.xaml">
<Application.Resources>
<ResourceDictionary>
<ResourceDictionary.MergedDictionaries>
<ResourceDictionary Source="/Wpf_Themes.ControlLibrary;component/ResourceDictionaries/Brushes/DefaultBlueTheme.xaml"/>
<ResourceDictionary Source="/Wpf_Themes.ControlLibrary;component/ResourceDictionaries/BaseControlStyles/ButtonStyle.xaml"/>
</ResourceDictionary.MergedDictionaries>
</ResourceDictionary>
</Application.Resources>
</Application>
and resources are now located correctly using the StaticResource

Static resource references are resolved at parse time (for the most part), whereas dynamic references are resolved at run time. This means a static reference can only be used if the resource has been parsed before the reference, whereas a dynamic reference can be used as a forward reference for a resource that is defined later.
Source: http://drwpf.com/blog/category/resources/
When the two ResourceDictionaries are in a separte Assembly and you reference them at the same time I would guess that this processing happens at the same time. Whereas if you load them in App.xaml directly it is ensured that they are loaded in the right order.
So the Resources of your first Dictionary are not available to the second Dictionary since you include them in the same Dictionary.
There is two ways to solve the Problem. Either you use DynamicResources which are evalutated at runtime (like you already tried).
Another solution if you now the hyrachie of your Resource Dictionaries you can do several levels. Like:
<Application x:Class="WPF_Theme.App"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
StartupUri="MainWindow.xaml">
<Application.Resources>
<ResourceDictionary>
<ResourceDictionary.MergedDictionaries>
<ResourceDictionary Source="pack://application:,,,/ControlLibrary;component/ResourceDictionaries/BaseLevel.xaml" />
<ResourceDictionary Source="pack://application:,,,/ControlLibrary;component/ResourceDictionaries/SecondLevel.xaml" />
</ResourceDictionary.MergedDictionaries>
</ResourceDictionary>
</Application.Resources>
BaseLevel.xaml
<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<ResourceDictionary.MergedDictionaries>
<ResourceDictionary Source="Brushes/DefaultBlueTheme.xaml" />
</ResourceDictionary.MergedDictionaries>
</ResourceDictionary>
SecondLevel.xaml
<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<ResourceDictionary.MergedDictionaries>
<ResourceDictionary Source="BaseControlStyles/ButtonStyle.xaml" />
</ResourceDictionary.MergedDictionaries>
</ResourceDictionary>
DefaultBlueTheme.xaml and ButtonStyle.xaml stays unchanged.
With this you would ensure that the different ResourceDictionaries are already there if you need them.
I hope that helps.

Setting window background color with XAML

I have a standard XAML styled window in WPF (< Window ....)
In this window I insert a resource dictionary
<Window.Resources>
<ResourceDictionary>
<ResourceDictionary.MergedDictionaries>
<ResourceDictionary Source="Style/Global.xaml" />
</ResourceDictionary.MergedDictionaries>
</ResourceDictionary>
</Window.Resources>
In the Global.xaml dicionary I have the following code:
<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<Style TargetType="Window">
<Setter Property="Background" Value="Red"/>
</Style>
</ResourceDictionary>
Nothing out of ordinary anywhere. Except it doesn't work, when I compile and run the app, the window background is shown in default white. BUT in the designer tab in Visual Studio where you can see the preview of your window, the background color is correctly changed to red. I don't understand.
I don't have any other styles inserted anywhere that could be overwriting the window's background color.
So how is it possible that in the preview tab it works correctly, but when i actually run the app, it doesn't? What am I doing wrong here?
Here is the entire window code:
<Window x:Class="Apptest.EditBook"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="EditBook" Height="300" Width="300">
<Window.Resources>
<ResourceDictionary>
<ResourceDictionary.MergedDictionaries>
<ResourceDictionary Source="Style/Global.xaml" />
<ResourceDictionary Source="Style/Controls.xaml" />
</ResourceDictionary.MergedDictionaries>
</ResourceDictionary>
</Window.Resources>
<Grid>
</Grid>
</Window>

OK... So this is because your window is actually a type deriving from Window...
public partial class EditBook : Window { }
Target type does not yet work with derived types so you will need to add a key to the style and add it to each window you create that you want to use the style for..
<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<Style TargetType="Window" x:Key="MyWindowStyle">
<Setter Property="Background" Value="Red"/>
</Style>
</ResourceDictionary>
then you will need to apply the style in the window...
<Window x:Class="Apptest.EditBook"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="EditBook" Height="300" Width="300" Style="{StaticResource MyWindowStyle}">
<Window.Resources>
<ResourceDictionary>
<ResourceDictionary.MergedDictionaries>
<ResourceDictionary Source="Style/Global.xaml" />
<ResourceDictionary Source="Style/Controls.xaml" />
</ResourceDictionary.MergedDictionaries>
</ResourceDictionary>
</Window.Resources>
<Grid>
</Grid>
</Window>
Hope this helps... there is no better solution from what I can see.