Hi Alexey,
The ShowMnemonicUnderlinesAlways property has been added to the BarItem only in version 4.x. Could you please consider upgrading to the latest version? If so, you can download it from the following location:
http://www2.syncfusion.com/Installs/v4.4.0.51/SyncfusionEssentialStudioSetup.exe
Unlock Key : Please contact our sales team (
[email protected] )
Thanks for your interest in Syncfusion products.
Best Regards,
Golda