Themes issue

Hello, Luke,

Indeed, the provided screenshot illustrates unexpected behavior since the themes are available in the components tray below the form. If you have installed the suite from the provided installation files, you will see the themes loaded in the Visual Studio toolbox. In order to use the Theme components, just drag and drop them from the VS Toolbox to the form. This will add a reference to the corresponding theme assembly in the project and will enable the theme in the ThemeName drop-down of all Telerik controls on the form. All you have to do afterwards is to set the needed theme from the ThemeName drop-down (in the smart tag) or programmatically.

If you don't see the themes available in the drop down, I suspect that there might be assemblies mismatch which is usually a common reason for such a behavior. I would like to ask you to check the references to all Telerik controls in your project and make sure that they are the same version considering the suffix as well (.20, .40, .48 etc.). Make sure that the version appearing in the Toolbox is the same as the version of the referred assemblies: 

Delete the license.licx file. After that, you should rebuild your project, close Visual Studio and open it again to make sure that no references are kept in the memory by Visual Studio.

In case you are still experiencing any further difficulties, note that you can apply the RadForm.ThemeName to all controls on the form via the form's smart tag:

Alternatively, as of R1 2021, it is possible to define which theme is your default theme (e.g. ControlDefault) for the controls even at design time. This can be defined in the App.config file. Additional information is available here:

https://docs.telerik.com/devtools/winforms/styling-and-appearance/default-theme#fluent-theme-as-default 

I hope this information helps. If you need any further assistance please don't hesitate to contact me. 

Regards,
Dess | Tech Support Engineer, Principal
Progress Telerik