Since Q2 2025, user defined Dark/Light/HighContrastResourcesPaths do not work - the custom resources are anot applied to the controls.

/// <summary>
/// Resource loader that provides the resource dictionaries with the brushes for the Telerik controls.
/// See https://docs.telerik.com/devtools/universal-windows-platform/common/teleriknamedbrushes.
/// </summary>
public sealed class TelerikResourceLoader : CustomXamlResourceLoader
{
    /// <inheritdoc/>
    protected override object GetResource(string resourceId, string objectType, string propertyName, string propertyType)
    {
        object result;
        if (resourceId == "DarkResourcesPath")
        {
            result = new Uri("ms-appx:///{ProjectName}/Assets/Themes/Dark_Telerik.xaml");
        }
        else if (
            resourceId == "LightResourcesPath" ||
            resourceId == "HighContrastResourcesPath")
        {
            result = new Uri("ms-appx:///{ProjectName}/Assets/Themes/Light_Telerik.xaml");
        }
        else
        {
            result = null;
        }
        return result;
    }
}

<ResourceDictionary.ThemeDictionaries>
    <ResourceDictionary x:Key="Light">
        <SolidColorBrush x:Key="TelerikGrid_BackgroundPointerOver" Color="Red" Opacity="0.25"/>
    </ResourceDictionary>
    <ResourceDictionary x:Key="Dark">
        <SolidColorBrush x:Key="TelerikGrid_BackgroundPointerOver" Color="Green" Opacity="0.25"/>
    </ResourceDictionary>
</ResourceDictionary.ThemeDictionaries>

Edit - indeed the Light/Dark/ResourcePaths are deleted from the generic files of telerk controls due to the following regression in WinUI App SDK 1.7.25:
https://github.com/microsoft/microsoft-ui-xaml/issues/10506 

Hello,

I have Telerik.WinUI.Controls v4.0.0 installed with Telerik.Licensing v1.6.5 with the extension installed and the license text file in the root folder of my project. However, I receive this message the first time a RadDataGrid is loaded on the UI on a secondary window. After closing and re-opening the window, the message doesn't show. When packaging for release, this doesn't seem to be an issue. The message is also stating the wrong version.

Create a combo box control that supports multi selecting, like the WPF version e.g.

https://docs.telerik.com/devtools/wpf/controls/radcombobox/features/multiple-selection

when the datagrid group the column ,the group header indent,but the general row don't indent .

look the following file.

Hi Team,

This is a request to add a Signature control to UI for WinUI. Where the user can use a Touch or Stylus input to add their signature to the app GUI. This signature can then be saved as either a bitmap or vector file.

Thank you,

Rodney

"Processing Resources failed" compile-time error is thrown when the following nuget packages are referenced together:

- Telerik.ReportViewer.WinUI
- Telerik.WinUI.Controls

It is enough only to reference the packages and try to build the project.

The error appears also if you try to reference the .dll instead of nuget packages. But only in case the Telerik.WinUI.Controls.dll file is not referenced from the installation folder of the Telerik Reporting product.

Error details:

1>WINAPPSDKGENERATEPROJECTPRIFILE : error : PRI175: 0x80073b0f - Processing Resources failed with error: Duplicate Entry.
1>WINAPPSDKGENERATEPROJECTPRIFILE : error : PRI222: 0x80073b0f - Unspecified error occurred.

I use a lot of very cool UI controls found in the Telerik UI UP control suite; our customers love these controls:

• RichText for HTML 5 presentation of email messages
• ScheduleView
• Diagrams - we use drawings for BP, WF and Data flows
• Docking - super popular
• Syntax Editor
• CardView
• SpreedSheet
• Expression Parser
• Expression Editor
• Layout control
• Expander
• Desktop Alert
• Transition Control
• TimeBar
• Wizard
• Window
• SplashSceeen
• Callout
• Drag and Drop Interactions
• Calendar
• Persistence Framework
• more..

You guys already know these capabilities don't exist as polished UI controls WinUI 3; we can't adapt and migrate to WinUI 3 / MAUI and lose these excellent presentation and interaction models. What other types of data and information would help your team to prioritize the development of these controls for WinUI 3. I know we can use some WinUI 3 UI control in our WPF apps, but going the other way is impossible. 

https://github.com/microsoft/WindowsAppSDK/discussions/465#discussioncomment-395712

Like many other technology companies out there in the wild, we aren't a UI Control development company as core skills focus on other technologies; however, we need the absolute very best 3rd part commercial grade and hi-fidelity UI controls to start with a base.  So for us, I'm not going to invest in a UI framework that turns the company into a Telerik - that's not what we do. Yes, we do develop custom controls, but it is the exception.