<%@ Page Title="Home Page" Language="C#" AutoEventWireup="true" 
CodeBehind="Default.aspx.cs" Inherits="FileDownloadExample._Default" %>

    

        Click the button to download a file
    
    

    

    

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
namespace FileDownloadExample
{
    public partial class _Default : Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
        }
        protected void Button1_Click(object sender, EventArgs e)
        {
            string filePath = "C:\\Users\\Admi\\Desktop\\abc.txt";
            FileInfo file = new FileInfo(filePath);
            if (file.Exists)
            {
                // Clear Rsponse reference
                Response.Clear();
                // Add header by specifying file name
                Response.AddHeader("Content-Disposition", "attachment; filename=" + file.Name);
                // Add header for content length
                Response.AddHeader("Content-Length", file.Length.ToString());
                // Specify content type
                Response.ContentType = "text/plain";
                // Clearing flush
                Response.Flush();
                // Transimiting file
                Response.TransmitFile(file.FullName);
                Response.End();
            }
            else Label1.Text = "Requested file is not available to download";
        }
    }
}