ExitVehicle.cs

using System;
using System.Windows.Forms;
using GTA;

public class ExitVehicle : Script
{
    public ExitVehicle()
    {
        Tick += OnTick;
    }

    const float _HOLD_THRESHOLD = 0.25f;
    float holdTime = 0;

    void OnTick(object sender, EventArgs e)
    {
        Ped player = Game.Player.Character;

        if (player.IsAlive && player.IsInVehicle())
        {
            if (Game.IsControlPressed(2, GTA.Control.INPUT_VEH_EXIT))
            {
                holdTime += Game.LastFrameTime;
            }
            else if (holdTime > 0)
            {
                Vehicle vehicle = player.CurrentVehicle;
                if (holdTime >= _HOLD_THRESHOLD)
                {
                    // Exit vehicle, close car door, turn off engine
                    player.Task.LeaveVehicle(vehicle, true);
                }
                else
                {
                    // Exit vehicle, don't close car door, leave engine running (if player is driver)
                    player.Task.LeaveVehicle(vehicle, false);
                    bool isDriver = vehicle.GetPedOnSeat(VehicleSeat.Driver) == player;
                    if (isDriver)
                    {
                        vehicle.EngineRunning = true;
                    }
                }

                holdTime = 0;
            }
        }
    }
}