how resume able file download in asp.net with c# -> best way (for large files too)

Question

see the below handler :

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

namespace FileExplorer
{
    /// 

        

Answer 1

here is the answer!

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Text;
using System.IO;
using System.Threading;
using System.Security.Cryptography;

namespace NiceFileExplorer.Classes
{
    public class DownloadFile
    {
        public static bool DownloadFileMethod(HttpContext httpContext, string filePath, long speed)
        {
            bool ret = true;
            try
            {
                switch (httpContext.Request.HttpMethod.ToUpper())
                { //support Get and head method
                    case "GET":
                    case "HEAD":
                        break;
                    default:
                        httpContext.Response.StatusCode = 501;
                        return false;
                }
                if (!File.Exists(filePath))
                {
                    httpContext.Response.StatusCode = 404;
                    return false;
                }
                //#endregion

                var fileInfo = new FileInfo(filePath);

                long startBytes = 0;
                int packSize = 1024 * 10; //read in block，every block 10K bytes
                string fileName = Path.GetFileName(filePath);
                FileStream myFile = new FileStream(filePath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite);
                BinaryReader br = new BinaryReader(myFile);
                long fileLength = myFile.Length;

                int sleep = (int)Math.Ceiling(1000.0 * packSize / speed);//the number of millisecond
                string lastUpdateTiemStr = File.GetLastWriteTimeUtc(filePath).ToString("r");
                string eTag = HttpUtility.UrlEncode(fileName, Encoding.UTF8) + lastUpdateTiemStr;

                //validate whether the file is too large
                if (myFile.Length > Int32.MaxValue)
                {
                    httpContext.Response.StatusCode = 413;
                    return false;
                }

                if (httpContext.Request.Headers["If-Range"] != null)
                {

                    if (httpContext.Request.Headers["If-Range"].Replace("\"", "") != eTag)
                    {
                        httpContext.Response.StatusCode = 412;
                        return false;
                    }
                }
                //#endregion

                try
                {

                    httpContext.Response.Clear();
                    httpContext.Response.Buffer = false;
                    httpContext.Response.AddHeader("Content-MD5", GetMD5Hash(fileInfo));
                    httpContext.Response.AddHeader("Accept-Ranges", "bytes");
                    httpContext.Response.AppendHeader("ETag", "\"" + eTag + "\"");
                    httpContext.Response.AppendHeader("Last-Modified", lastUpdateTiemStr);
                    httpContext.Response.ContentType = "application/octet-stream";
                    httpContext.Response.AddHeader("Content-Disposition", "attachment;filename=" +

                    HttpUtility.UrlEncode(fileName, Encoding.UTF8).Replace("+", "%20"));
                    httpContext.Response.AddHeader("Content-Length", (fileLength - startBytes).ToString());
                    httpContext.Response.AddHeader("Connection", "Keep-Alive");
                    httpContext.Response.ContentEncoding = Encoding.UTF8;
                    if (httpContext.Request.Headers["Range"] != null)
                    {
                        httpContext.Response.StatusCode = 206;
                        string[] range = httpContext.Request.Headers["Range"].Split(new char[] { '=', '-' });
                        startBytes = Convert.ToInt64(range[1]);
                        if (startBytes < 0 || startBytes >= fileLength)
                        {
                            return false;
                        }
                    }
                    if (startBytes > 0)
                    {
                        httpContext.Response.AddHeader("Content-Range", string.Format(" bytes {0}-{1}/{2}", startBytes, fileLength - 1, fileLength));
                    }
                    //#endregion

                    //send data
                    br.BaseStream.Seek(startBytes, SeekOrigin.Begin);
                    int maxCount = (int)Math.Ceiling((fileLength - startBytes + 0.0) / packSize);//download in block
                    for (int i = 0; i < maxCount && httpContext.Response.IsClientConnected; i++)
                    {
                        httpContext.Response.BinaryWrite(br.ReadBytes(packSize));
                        httpContext.Response.Flush();
                        if (sleep > 1) Thread.Sleep(sleep);
                    }
                    //#endregion
                }
                catch
                {
                    ret = false;
                }
                finally
                {
                    br.Close();
                    myFile.Close();
                }
            }
            catch
            {
                ret = false;
            }
            return ret;
        }

        private static string GetMD5Hash(FileInfo file)
        {
            var stream = file.OpenRead();
            MD5 md5 = new MD5CryptoServiceProvider();
            byte[] retVal = md5.ComputeHash(stream);
            stream.Close();

            var sb = new StringBuilder();
            for (int i = 0; i < retVal.Length; i++)
            {
                sb.Append(retVal[i].ToString("x2"));
            }
            return sb.ToString();
        }

    }
}