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