RadGroupBox supports mnemonics out of the box. When its mnemonic key is pressed the first control in the group box is focused automatically.
In order to activate this functionality you should specify the character that will be used for a given control by placing the & character before the desired symbol.
radGroupBox1.Text = "Te&st";
RadGroupBox1.Text = "Te&st"
UseMnemonic is a boolean property which controls whether the & character is displayed as the symbol itself or whether it is used to designate a mnemonic (visualized as an underscore). Its default value is true i.e. mnemonics are used by default.