Thank you for getting back to us.
I suppose you are regarding the drop down menu part. If so, you should make a separate theme for the RadDropDownButton. Set its ThemeName to be the same as the ThemeName of the theme for RadTabStrip.
Then, when you load these themes in your application and set the theme for the RadTabStrip, the theme for the menu part will be applied automatically.
I am attaching a sample project to demonstrate this behavior. If you have additional questions, feel free to contact me.
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