To press a special character use Android.PressKeyCode action. The list of key codes is available here. Let's see a few examples:

// press ENTER button
Android.PressKeyCode(66);

// press SEARCH button
Android.PressKeyCode(84);

https://developer.android.com/reference/android/view/KeyEvent#KEYCODE_ENTER

https://developer.android.com/reference/android/view/KeyEvent#KEYCODE_SEARCH