【.Net码农】C#实现文件下载

1，Http 协议中有专门的指令来告知浏览器, 本次响应的是一个需要下载的文件. 格式如下:
Content-Disposition: attachment;filename=filename.ext
以上指令即标记此次响应流是附件,且附件文件名为 filename.ext
注意：
(1): 中文文件名需要进行URLEncode编码, 否则在IE 6 下会提示是”无法识别的文件”.

但经实际测试,在Chrome下不进行URLEncode编码, 也能正常显示.

(2): 文件名不能有空格, 否则也会被认为是”无法识别的文件”.

(3): [ASP.Net中] 向响应流中添加该指令必须使用 response.AddHeader() 函数; 使用

response.Header.Add() 则会报错.

下面是一个实现下载文件功能的函数：

       /// <summary>        /// 使用微软的TransmitFile下载文件        /// </summary>        /// <param name="filePath">服务器相对路径</param>        public void TransmitFile(string filePath)        {            try            {                filePath = Server.MapPath(filePath);                if (File.Exists(filePath))                {                    FileInfo info = new FileInfo(filePath);                    long fileSize = info.Length;                    HttpContext.Current.Response.Clear();                                                            //指定Http Mime格式为压缩包                    HttpContext.Current.Response.ContentType = "application/x-zip-compressed";                                        // Http 协议中有专门的指令来告知浏览器, 本次响应的是一个需要下载的文件. 格式如下:                    // Content-Disposition: attachment;filename=filename.txt                    HttpContext.Current.Response.AddHeader("Content-Disposition", "attachment;filename=" + Server.UrlEncode(info.FullName));                    //不指明Content-Length用Flush的话不会显示下载进度                       HttpContext.Current.Response.AddHeader("Content-Length", fileSize.ToString());                    HttpContext.Current.Response.TransmitFile(filePath, 0, fileSize);                    HttpContext.Current.Response.Flush();                }            }            catch            { }            finally            {                HttpContext.Current.Response.Close();            }        }

2 下面是使用WriteFile实现下载

        /// <summary>        /// 使用WriteFile下载文件          /// </summary>        /// <param name="filePath">相对路径</param>        public void WriteFile(string filePath)        {            try            {                filePath = Server.MapPath(filePath);                if (File.Exists(filePath))                {                    FileInfo info = new FileInfo(filePath);                    long fileSize = info.Length;                    HttpContext.Current.Response.Clear();                    HttpContext.Current.Response.ContentType = "application/octet-stream";                    HttpContext.Current.Response.AddHeader("Content-Disposition", "attachement;filename=" + Server.UrlEncode(info.FullName));                    //指定文件大小                       HttpContext.Current.Response.AddHeader("Content-Length", fileSize.ToString());                    HttpContext.Current.Response.WriteFile(filePath, 0, fileSize);                    HttpContext.Current.Response.Flush();                }            }            catch            { }            finally            {                HttpContext.Current.Response.Close();            }        }

3，下面是分块实现下载：

        /// <summary>        /// 使用OutputStream.Write分块下载文件          /// </summary>        /// <param name="filePath"></param>        public void WriteFileBlock(string filePath)        {            filePath = Server.MapPath(filePath);            if (!File.Exists(filePath))            {                return;            }            FileInfo info = new FileInfo(filePath);            //指定块大小               long chunkSize = 4096;            //建立一个4K的缓冲区               byte[] buffer = new byte[chunkSize];            //剩余的字节数               long dataToRead = 0;            FileStream stream = null;            try            {                //打开文件                   stream = new FileStream(filePath, FileMode.Open, FileAccess.Read, FileShare.Read);                                dataToRead = stream.Length;                //添加Http头                   HttpContext.Current.Response.ContentType = "application/octet-stream";                HttpContext.Current.Response.AddHeader("Content-Disposition", "attachement;filename=" + Server.UrlEncode(info.FullName));                HttpContext.Current.Response.AddHeader("Content-Length", dataToRead.ToString());                while (dataToRead > 0)                {                    if (HttpContext.Current.Response.IsClientConnected)                    {                        int length = stream.Read(buffer, 0, Convert.ToInt32(chunkSize));                        HttpContext.Current.Response.OutputStream.Write(buffer, 0, length);                        HttpContext.Current.Response.Flush();                        HttpContext.Current.Response.Clear();                        dataToRead -= length;                    }                    else                    {                        //防止client失去连接                           dataToRead = -1;                    }                }            }            catch (Exception ex)            {                HttpContext.Current.Response.Write("Error:" + ex.Message);            }            finally            {                if (stream != null)                {                    stream.Close();                }                HttpContext.Current.Response.Close();            }        }