Help with Attachment c#

using System;
using System.Collections.Generic;
using System.Text;
using System.IO;
using System.Windows;
using System.Web.Mail;

namespace TfL
{
    class Program
    {
        static void Main(String[] args)
        {
            System.IO.FileInfo info = new System.IO.FileInfo("c:\\Source\\LNS_IS.txt");

            if (File.Exists("c:\\Source\\LNS_IS.txt") && (info.Length > 0))
            {
                MailMessage oMsg = new MailMessage();
                oMsg.From = "Happy@test.com";
                oMsg.To = "246@gmail.com";
                oMsg.Subject = "Unattended Mailbox do not reply";
                oMsg.BodyFormat = MailFormat.Html;

                // ADD AN ATTACHMENT.
                String sFile = @"C:\Source\LNS_IS.TXT";
                MailAttachment oAttch = new MailAttachment(sFile, MailEncoding.Base64);

                oMsg.Attachments.Add(oAttch);

                //SMTP server.
                SmtpMail.SmtpServer = "vmtestmac";
                SmtpMail.Send(oMsg);

                oMsg = null;
                oAttch = null;


                //move the file now email is sent
                string sourceFile = @"C:\Source\LNS_IS.txt";
                string destinationFile = @"C:\Archive\LNS_IS.txt";
                System.IO.File.Move(sourceFile, destinationFile);

                //shows message for testing
                global::System.Windows.Forms.MessageBox.Show("sending File Exists ");

            }
            else
            {
                MailMessage oMsg = new MailMessage();
                oMsg.From = "Happy@test.com";
                oMsg.To = "246@gmail.com";
                oMsg.Subject = "Unattended Mailbox do not reply";
                oMsg.BodyFormat = MailFormat.Html;

                //SMTP server.
                SmtpMail.SmtpServer = "vmtestmac";
                SmtpMail.Send(oMsg);

                oMsg = null;

                //shows message for testing
                global::System.Windows.Forms.MessageBox.Show("sending file not exist");
            }

            //checking if file has any data


            if (info.Length < 1)
            {
                //move the file 
                string sourceFile = @"C:\Source\LNS_IS.txt";
                string destinationFile = @"C:\Baddata\LNS_IS.txt";
                System.IO.File.Move(sourceFile, destinationFile);

             }


        }

    }
}