The keys argument can specify any single key or any key combined with ALT, CTRL, or SHIFT (or any combination of those keys). For more information, see Walkthrough: Calling Windows APIs. Because there is no managed method to activate another application, you can either use this class within the current application, manually select the window to send the keys to, or use Windows API methods, such as FindWindow and SetForegroundWindow, to force focus on other applications.
