Ways to Select a Windows Forms Button Control
A Windows Forms button can be selected in the following ways:
Use a mouse to click the button.
Invoke the button's Click event in code.
Move the focus to the button by pressing the TAB key, and then choose the button by pressing the SPACEBAR or ENTER.
Press the access key (ALT + the underlined letter) for the button. For more information about access keys, see How to: Create Access Keys for Windows Forms Controls.
If the button is the "accept" button of the form, pressing ENTER chooses the button, even if another control has the focus — except if that other control is another button, a multi-line text box, or a custom control that traps the enter key.
If the button is the "cancel" button of the form, pressing ESC chooses the button, even if another control has the focus.
Call the PerformClick method to select the button programmatically.