how to trigger the beep sound of the zk4500 biometric finger priint reader

You've to have referenced the SDK COM and namespace ZKFPengController first

and an object called ZKFPEngX1 which is going to use reference On finger touching

private void ZKFPEngX1_OnFingerTouching(object sender, EventArgs e)
        {
            lblState.Text = "TOUCH";
            ZKFPEngX1.ControlSensor(13, 1);
            ZKFPEngX1.ControlSensor(13, 0);
        }

FirstNumber 13 means BEEP sound
SecondNumber 1 means Begin
SecondNumber 0 means End

that worked for me in VS C# 2013

best regards