using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Runtime.InteropServices;

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        [DllImport("kernel32.dll")]
        static extern int Sleep(long dwMilliseconds);

        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            lbltxt.Text = "calling windows API calls by interopservices....";
            MessageBox.Show("start sleeping for 5000..................");
            Sleep(1000);
            MessageBox.Show("end.............");
        }
    }
}