Develop Reference

WPF Resources in class library in .NET 5

Before, in .NET Framework, when I created a WPF class library, I had my App.xaml (set as Application definition) referencing my resource dictionaries like that:
<Application xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation">
<Application.Resources>
<ResourceDictionary>
<ResourceDictionary.MergedDictionaries>
<ResourceDictionary Source="ResourceDictionary1.xaml" />
<ResourceDictionary Source="ResourceDictionary2.xaml" />
<ResourceDictionary Source="ResourceDictionary3.xaml" />
</ResourceDictionary.MergedDictionaries>
</ResourceDictionary>
</Application.Resources>
</Application>
However, now, with .NET 5, I get this compilation error:
Library project file cannot specify ApplicationDefinition element.
So that message means I can't have an App.xaml file in a class library anymore. But now, I don't know how to define my resources globally in a class library. Isn't there any way to do this without referencing the dictionaries in each and every XAML file in the project?
Edit: It's not about the Source syntax. The path is correct and everything compiles perfectly if I set the project to Windows Application instead of Class Library.

refering to that github issue : https://github.com/dotnet/wpf/issues/2812#issuecomment-607537794
In an SDK style WindowsDesktop project,
*.xaml are all treated as Page items by default, unless they are named App.xaml (C#) or Application.xaml (VB).
App.xaml/Application.xaml is treated as ApplicationDefinition by default.
<!--
Disables automatic globbing of App.xaml/Application.xaml into
ApplicationDefinition item
App.xaml/Application.xaml would now get treated as any other *.xaml file
(typically, a Page)
-->
<PropertyGroup>
<EnableDefaultApplicationDefinition>false</EnableDefaultApplicationDefinition>
</PropertyGroup>
Worth a try.

For me works the following: If you have library-project with resources (i.e. namespace "Project.Resources") and have presentation-project (i.e. namespace "Project.Presentation"):
<Application x:Class="Project.Presentation.App"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation">
<Application.Resources>
<ResourceDictionary>
<ResourceDictionary.MergedDictionaries>
<ResourceDictionary Source="/Project.Resources;Dictionary.xaml" />
</ResourceDictionary.MergedDictionaries>
</ResourceDictionary>
</Application.Resources>
</Application>
Don't forget to add reference to "Project.Resources" in "Project.Presentation".

Window style not visible in designer

I created a Window style (WPF) and added it as a dll to my project
this style shows corretly when i run the program but doesn't show up in the designer.
I googled already but none of the solutions there are working
Test 1:
// Window //
Style="{DynamicResource HVE_Window}"
// Window.Resources //
<ResourceDictionary.MergedDictionaries>
<ResourceDictionary Source="pack://application:,,,/GlobalHive.Styles;component/HiveWindow.xaml"/>
</ResourceDictionary.MergedDictionaries>
Result:
Error: 'Window' TargetType doesn not match type of element 'WindowInstance'
-> But it runs and display correctly there
Test 2:
// Window //
Style="{DynamicResource MyWindow}"
// Window.Resources //
<ResourceDictionary.MergedDictionaries>
<ResourceDictionary Source="pack://application:,,,/GlobalHive.Styles;component/HiveWindow.xaml"/>
</ResourceDictionary.MergedDictionaries>
<Style x:Key="MyWindow" TargetType="{x:Type Window}" BasedOn="{StaticResource HVE_Window}" />
Result:
No Error:
Still doesn't display in the designer, still shows up if i run the program
Test 3:
Both versions but added to application resources
How it should look:
How it looks inside the designer:

You can sometimes find that resources from a control library are not loaded at design time, despite whatever you put in app.xaml to try and load the things.
MS created a mechanism for Blend which you can use in visual studio since it's the blend designer.
This uses a "special" resource dictionary called DesignTimeResources.xaml
This will only be used at design time.
Add one to the Properties of your problem exe project.
With exactly that name.
Put all your merges into that.
eg this is one of mine from my MapEditor project that uses numerous resources from UILib. UILib is a control library with all sorts of UI stuff in it.
<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:MapEditor">
<ResourceDictionary.MergedDictionaries>
<ResourceDictionary Source="pack://application:,,,/UILib;component/Resources/Geometries.xaml"/>
<ResourceDictionary Source="pack://application:,,,/UILib;component/Resources/ControlTemplates.xaml"/>
<ResourceDictionary Source="pack://application:,,,/UILib;component/Resources/FontResources.xaml"/>
<ResourceDictionary Source="pack://application:,,,/UILib;component/Resources/UILibResources.xaml"/>
<ResourceDictionary Source="/Views/Drawing/Terrain/Resources/CityResources.xaml"/>
<ResourceDictionary Source="/Resources/MapEditorResources.xaml"/>
</ResourceDictionary.MergedDictionaries>
</ResourceDictionary>
Unload your csproj ( right click in solution explorer), edit it and find the node for that resource dictionary.
Change it to:
<Page Include="Properties\DesignTimeResources.xaml">
<SubType>Designer</SubType>
<Generator>MSBuild:Compile</Generator>
<ContainsDesignTimeResources>true</ContainsDesignTimeResources>
</Page>
Reload the project, close and re-open visual studio.
Your styles should now apply.

Using a Loading Indicator for WPF application

I'm relatively new to WPF and I would like to add a loading indicator. I found https://github.com/100GPing100/LoadingIndicators.WPF which has some nice pre-made loading indicators and I installed the NuGet Package for it but I'm having a hard time implementing them to my window.
So I added
<Window ...
xmlns:loadin="clr-namespace:LoadingIndicators.WPF;assembly=LoadingIndicators.WPF"
...
>
Window.Resources>
<ResourceDictionary>
<ResourceDictionary.MergedDictionaries>
<ResourceDictionary Source="pack://application:,,,/LoadingIndicators.WPF;component/Styles/LoadingDoubleBounce.xaml"/>
</ResourceDictionary.MergedDictionaries>
</ResourceDictionary>
</Window.Resources>
But when I try to add one of the loading indicators to my grid I get an error on the dynamic resource
<Grid x:Name="TagLoadingIndicator" Panel.ZIndex="1">
<loadin:LoadingIndicator SpeedRatio="{Binding SpeedRatio}" IsActive="{Binding IsDoubleBounceActive}" Style="{DynamicResource LoadingIndicatorDoubleBounceStyle}"/>
</Grid>
The error I get is
The resource "LoadingIndicatorDoubleBounceStyle" could not be
resolved.
From what I saw in other websites, I am adding it to the ResourceDictionary correctly... And I'm assuming that by installing the NuGet package, I have the resource already defined. I can still run the application but the indicator is missing. What am I missing?
Thank you

That key exists in the Styles.xaml file. So add a reference to it in your resources.
<Window.Resources>
<ResourceDictionary>
<ResourceDictionary.MergedDictionaries>
<ResourceDictionary Source="pack://application:,,,/LoadingIndicators.WPF;component/Styles/LoadingDoubleBounce.xaml"/>
<ResourceDictionary Source="pack://application:,,,/LoadingIndicators.WPF;component/Styles.xaml"/>
</ResourceDictionary.MergedDictionaries>
</ResourceDictionary>
</Window.Resources>

Using (merged) Resource Dictionary in C# Class Library Project

How can I use a (merged) WPF Resource Dictionary in a C# class library project?
Here is what I did:
In my C# class library project I have a file Dictionary1.xaml like that:
<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
>
<Style x:Key="PluginFrameBorderStyle">
...
</Style>
</ResourceDictionary>
Then, I have a UserControl file UserControl1.xaml where I try to use the Dictionary like that:
<UserControl x:Class="EditorPackageA.BackboneMemberB1Editor.BackboneMemberB1Editor"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
mc:Ignorable="d"
xmlns:local="clr-namespace:EditorPackageA.EditorBase"
xmlns:prism="http://www.codeplex.com/prism" d:DesignWidth="690.4" d:DesignHeight="460.12">
<UserControl.Resources>
<ResourceDictionary>
<ResourceDictionary.MergedDictionaries>
<ResourceDictionary Source="/Dictionary1.xaml"/>
</ResourceDictionary.MergedDictionaries>
</ResourceDictionary>
</UserControl.Resources>
...
</UserControl>
The project compiles but at runtime I get the error:
with the exception detail:
The same approach works when applied within a WPF project rather than a Class Library project.
What might be the solution here?
Important Addendum:
During design-time I see the effect of the used style that is embedded via the ResourceDictionary, hence the URI of the style and the dictionary must be correct!?

Try to use so called pack URI. I think that you have to explicitly specify where the resource dictionary is located.
<ResourceDictionary Source="pack://application:,,,/TheNameOfClassLibrary;component/Dictionary1.xaml"/>
In the case of a WPF project your approach works because WPF engine by default looks for resource in the assembly being executed (in exe).

You should refer/link the ResourceDictionary xml file to the Source attribute with assembly and component name.
Use relative path as follows:
<ResourceDictionary Source="../Dictionary1.xaml" />
If it is not working, then try PACK URL
<ResourceDictionary Source="pack://application:,,,/Your.Base.AssemblyName;component/DictionaryFolder/Dictionary1.xaml" />
Hope it helps you

You probably need to merge your library's resource dictionary in your application resources. You need to edit your App.xaml file and add something like:
<Application.Resources>
<ResourceDictionary>
<ResourceDictionary.MergedDictionaries>
<ResourceDictionary Source="pack://application:,,,/YourAssembly;component/Dictionary1.xaml" />
</ResourceDictionary.MergedDictionaries>
</ResourceDictionary>
</Application.Resources>

XamlParseException when attempting to open a WPF Window from Winforms

I have a single Winforms project and multiple WPF projects in one solution. From the Winform application I'd like to open one of the WPF Windows (it's a MetroWindow from Mahapps, if it matters).
After looking at the accepted answer to this stackoverflow question I ended up with this piece of code:
OpenWPFAppButton_Click(object sender, EventArgs e)
{
WPFApp wpfApp = new WPFApp();
ElementHost.EnableModelessKeyboardInterop(wpfApp);
wpfApp.Show();
}
Unfortunately if I click the button a XamlParseException occurs, which points to the first Style="{StaticResource ... }" line in WPFApp.xaml (the Main Xaml File).
Does this mean I cannot open WPF Windows from Winforms that include static resources? Or am I missing something simple here?
EDIT: Here is the content of the App.xaml file:
<Application x:Class="WPFAppProjectName.App"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:system="clr-namespace:System;assembly=mscorlib"
StartupUri="WPFApp.xaml">
<Application.Resources>
<ResourceDictionary>
<ResourceDictionary.MergedDictionaries>
<ResourceDictionary Source="pack://application:,,,/Selen.Wpf.SystemStyles;component/ButtonStyles.xaml"/>
<ResourceDictionary Source="pack://application:,,,/Selen.Wpf.SystemStyles;component/MenuStyles.xaml"/>
<ResourceDictionary Source="pack://application:,,,/Selen.Wpf.SystemStyles;component/TextBoxStyles.xaml"/>
</ResourceDictionary.MergedDictionaries>
</ResourceDictionary>
</Application.Resources>

It is most likely that some common resources are defined in the App.xaml. That file isn't loaded when running through Windows Forms and thus those resources are unavailable. Hence you get this error.
You could include the resource definitions in the Window.xaml files, or an own common style resource file (aka Resource Dictionary) which is included in every Window.