SendKeys の代わりに WinAPI を使用できます。
[DllImport("user32.dll", SetLastError = true)]
static extern void keybd_event(byte bVk, byte bScan, uint dwFlags, UIntPtr dwExtraInfo);
public static void PressKey(Keys key, bool up) {
const int KEYEVENTF_EXTENDEDKEY = 0x1;
const int KEYEVENTF_KEYUP = 0x2;
if (up) {
keybd_event((byte) key, 0x45, KEYEVENTF_EXTENDEDKEY | KEYEVENTF_KEYUP, (UIntPtr) 0);
}
else {
keybd_event((byte) key, 0x45, KEYEVENTF_EXTENDEDKEY, (UIntPtr) 0);
}
}
void TestProc() {
PressKey(Keys.ControlKey, false);
PressKey(Keys.P, false);
PressKey(Keys.P, true);
PressKey(Keys.ControlKey, true);
}