Find no of seconds between two dates

using System;

using System.Collections.Generic;

using System.Linq;

using System.Web;

using System.Web.UI;

using System.Web.UI.WebControls;

using System.IO;

namespace API

{

    public partial class datediff : System.Web.UI.Page

    {

        protected void Page_Load(object sender, EventArgs e)

        {

           // Sub();

            Sub1();

        }

        public void Sub()

        {

            DateTime dt1 = DateTime.Now;

            DateTime dt2 = new DateTime(2003, 4, 15);

            TimeSpan ts = dt1.Subtract(dt2);

            Response.Write(ts);

        }

        public void Sub1()

        {

            string strFileNAme = Server.MapPath(string.Format("~/cp.txt"));

            Response.Write(strFileNAme);

            Response.Write("</br>");

            FileInfo fi = new FileInfo(strFileNAme);

            DateTime dtSession = fi.LastWriteTime;

            Response.Write(dtSession);

            Response.Write("</br>");

            DateTime dt4 = DateTime.Now;

            Response.Write(dt4);

            Response.Write("</br>");

            TimeSpan diff = dt4 - dtSession;

            double seconds = diff.TotalSeconds;

            Response.Write(seconds);

        }

    }

       

}

OUTPUT:

D:\API\API\cp.txt

9/25/2013 3:13:47 PM

9/25/2013 4:19:23 PM

3935.7701132