[Solved] Problems with the UI for WPF 2026.2.520 release

[Joe]

I just updated all of my Telerik UI for WPF assemblies from 2026.1.415 to 2026.2.520.  It caused two problems.

First, someone apparently forgot to release a corresponding version of the French-specific version of

     Telerik.Windows.Controls.for.Wpf.Xaml

Because now my build tells me that the Telerik NuGet server has no such 2026.2.520 version of

    Telerik.Windows.Controls.for.Wpf.Xaml.fr

So I can either remove that ".fr" version assembly from all my projects or decline to update everything.

Secon -- after I tried to remove that assembly and build --  I started getting all sorts of warnings about CLS-Compliance.  For example, one of my controls exposes this DependencyProperty of type `Telerik.Windows.Controls.ChartSelectionMode`

 

    public ChartSelectionMode SelectionMode
    {
        get => (ChartSelectionMode)GetValue(SelectionModeProperty);
        set => SetValue(SelectionModeProperty, value);
    }

But with the new release, this code causes the following compiler warning

2>C:\Users\joe\source\repos\Main\Mobile\Modules\Modules.Common\Controls\PlotControl.xaml.cs(372,31,372,44): error CS3003: Type of 'PlotControl.SelectionMode' is not CLS-compliant

I didn't change my code and the type "ChartSelectionMode is just an enum.  I don't understand how this can be happening.  I am getting similar warnings about many such Telerik types.  Including

• Telerik.Windows.Controls.ChartView.SurfaceSeries3DColorizer
• Telerik.Windows.Controls.ChartView.ChartAnnotationDescriptorSelector
• Telerik.Windows.Controls.ChartSelectionMode
  

Did something change in these types?  I know how to disable the warning or put a [CLSCompliant(false)] tag where it needs to go but I would like to understand what changed.

[Nadya | Tech Support Engineer]

Hello, Joe,

Telerik.Windows.Controls.for.Wpf.Xaml.fr

Starting from the Q2 2026 release, the satellite NuGet packages for built-in localization support, such as Telerik.Windows.Controls.for.Wpf.fr, are no longer produced as separate packages. The satellite assemblies are included in the Telerik.Windows.Controls.for.Wpf Nuget package. This change has been announced in the Release History. 

With version 2026.2.520, you should now download Telerik.Windows.Controls.for.Wpf nuget package to get the Telerik.Windows.Controls.for.Wpf.Xaml.fr assembly.

ChartSelectionMode property

As to the ChartSelectionMode property, we have not included any changes to it in the latest release. Can you confirm that you refer to the RadChartView components, which are actively supported (not to the old RadChart, which is no longer supported in our suite).

RadChartView is available in Telerik.Windows.Controls.Chart dll. You need to refer to this dll in your project. 

The issue might be that the Chart assembly is missing the [assembly: CLSCompliant(true)] attribute by default. When your consumer assembly is marked as CLS-compliant and exposes a public property of type ChartSelectionMode, the compiler warns because that type comes from an assembly that hasn't declared itself CLS-compliant.

Possibly the CS3003 warning ("Type of 'PlotControl.SelectionMode' is not CLS-compliant") occurs because:
- Your consuming assembly is marked [assembly: CLSCompliant(true)].
- You expose a public property of type ChartSelectionMode.
- The Chart assembly that defines ChartSelectionMode was not marked [assembly: CLSCompliant(true)].

When a CLS-compliant assembly exposes a type from a non-CLS-compliant assembly, the compiler flags it. The possible solution would be to add [CLSCompliant(true)] to the enum itself:

[System.CLSCompliant(true)]
public enum ChartSelectionMode

However, it is difficult for me to determine why exactly these warnings happen on your side, and I can provide only suggestions. If you need further assistance, it would be greatly appreciated if you could provide a sample project that can recreate those warnings and provide the project to me for further investigation.

It is also possible to suppress the CS3003 warnings in the consumer's project, if you want to, by using: <NoWarn>$(NoWarn);CS3003</NoWarn>

I hope this information helps. Please let me know if I can assist you further.

Regards,
Nadya | Tech Support Engineer
Progress Telerik

[Joe]

Ok this is all great.  Thank you for such a detailed reply.