How to implement key event for button click event

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C#

Hi everybody!
I'm writing a virtual keyboard, and i have a problem.
As we know when press a key on real keyboard, control which focused will receive key event
i don't want to writing code handle, i want to send keycode for textbox, and textbox will perform a action with this keycode.
Ex: you focus in a Multi line textbox, when you press key Enter. textbox will add 1 line and show cursor at that line.
.Textbox will receive Enter 's key code , after that textbox will perform 1 action with this Enter keycode.

so now i want to know that how to implement key event from buttton click event for a control.
Please help me! Thanks!!!
Kind regards.
Sugia