LockWorkStation.cs

using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.InteropServices;

namespace LockWorkStation
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Locking WorkStation...");
            LockWorkStation();
        }

        [DllImport("user32.dll")]
        static extern bool LockWorkStation();
    }
}