public class DownLoadHelper    {               /// <summary>        /// WriteFile实现下载--测试通过        /// </summary>        /// <param name="filePath">文件路径</param>        public static void  DownLoadWithWriteFile(string filePath)        {            string fileName = Path.GetFileName(filePath);//客户端保存的文件名            FileInfo fileInfo = new FileInfo(filePath);            HttpContext.Current.Response.Clear();            HttpContext.Current.Response.ClearContent();            HttpContext.Current.Response.ClearHeaders();            HttpContext.Current.Response.AddHeader("Content-Disposition", "attachment;filename=" + fileName);            HttpContext.Current.Response.AddHeader("Content-Length", fileInfo.Length.ToString());            HttpContext.Current.Response.AddHeader("Content-Transfer-Encoding", "binary");            HttpContext.Current.Response.ContentType = "application/octet-stream";            HttpContext.Current.Response.ContentEncoding = System.Text.Encoding.GetEncoding("gb2312");            HttpContext.Current.Response.WriteFile(fileInfo.FullName);            HttpContext.Current.Response.Flush();            HttpContext.Current.Response.End();        }        /// <summary>        /// WriteFile分块下载--测试通过        /// </summary>        /// <param name="filePath">文件路径</param>        public static void DownLoadWithWriteFileByStep(string filePath)        {            string fileName = Path.GetFileName(filePath);//客户端保存的文件名            System.IO.FileInfo fileInfo = new System.IO.FileInfo(filePath);            if (fileInfo.Exists)            {                const long ChunkSize = 102400;//100K 每次读取文件，只读取100K，这样可以缓解服务器的压力                byte[] buffer = new byte[ChunkSize];                HttpContext.Current.Response.Clear();                System.IO.FileStream iStream = System.IO.File.OpenRead(filePath);                long dataLengthToRead = iStream.Length;//获取下载的文件总大小                HttpContext.Current.Response.ContentType = "application/octet-stream";                HttpContext.Current.Response.AddHeader("Content-Disposition", "attachment; filename=" + HttpUtility.UrlEncode(fileName));                while (dataLengthToRead > 0 && HttpContext.Current.Response.IsClientConnected)                {                    int lengthRead = iStream.Read(buffer, 0, Convert.ToInt32(ChunkSize));//读取的大小                    HttpContext.Current.Response.OutputStream.Write(buffer, 0, lengthRead);                    HttpContext.Current.Response.Flush();                    dataLengthToRead = dataLengthToRead - lengthRead;                }                HttpContext.Current.Response.Close();            }        }        /// <summary>        /// 流方式下载--测试通过        /// </summary>        /// <param name="filePath">文件路径</param>        public static void DownLoadWithStream(string filePath)        {            string fileName = Path.GetFileName(filePath);//客户端保存的文件名            //以字符流的形式下载文件            FileStream fs = new FileStream(filePath, FileMode.Open);            byte[] bytes = new byte[(int)fs.Length];            fs.Read(bytes, 0, bytes.Length);            fs.Close();            HttpContext.Current.Response.ContentType = "application/octet-stream";            //通知浏览器下载文件而不是打开            HttpContext.Current.Response.AddHeader("Content-Disposition", "attachment;  filename=" + HttpUtility.UrlEncode(fileName, System.Text.Encoding.UTF8));            HttpContext.Current.Response.BinaryWrite(bytes);            HttpContext.Current.Response.Flush();            HttpContext.Current.Response.End();        }        /// <summary>        /// TransmitFile实现下载--测试通过        /// </summary>        /// <param name="filePath">文件路径</param>        public static void DownLoadWithTransmitFile(string filePath)        {            string fileName = Path.GetFileName(filePath);//客户端保存的文件名            /*         微软为Response对象提供了一个新的方法TransmitFile来解决使用Response.BinaryWrite         下载超过400mb的文件时导致Aspnet_wp.exe进程回收而无法成功下载的问题。         */            HttpContext.Current.Response.ContentType = "application/x-zip-compressed";            HttpContext.Current.Response.AddHeader("Content-Disposition", "attachment;filename="+ HttpUtility.UrlEncode(fileName, System.Text.Encoding.UTF8));            HttpContext.Current.Response.TransmitFile(filePath);        }    }
调用方法：

public void DownMap(string LinkUrl){string filePath = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "DownLoadSource\\1.txt");DownLoadHelper.DownLoadWithTransmitFile(filePath);}
前端:

function download(linkUrl) {            window.location.href = "http://www.mamicode.com/Home/DownMap?LinkUrl=" + linkUrl;        }