Closing form taking user confirmation in windows

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;

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_FormClosing(object sender, FormClosingEventArgs e)
        {
            DialogResult dr = MessageBox.Show("Are you sure you want to close this form?", "Confirmation of Form Closure", MessageBoxButtons.YesNo);
            if (dr == DialogResult.No) e.Cancel = true;
        }
    }
}