C#怎么实现文件下载功能

来源：互联网发布：民族知识知多少编辑：程序博客网时间：2024/05/16 18:52

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.

        /// <summary>
        /// TransmitFile实现下载
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        protected void btnTransmit_Click(object sender, EventArgs e)
        {
            /*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。
             * 代码如下：*/
            Response.ContentType = "application/x-zip-compressed";
            string FileName = "test.docx";
            //使用UTF-8对文件名进行编码
            Response.AppendHeader("Content-Disposition", "attachment;filename=\"" + HttpUtility.UrlEncode(FileName, System.Text.Encoding.UTF8) + "\"");
            Response.ContentType = "application/octet-stream";
            Response.AddHeader("Content-Disposition", "attachment;filename=" + FileName);
            string filename = Server.MapPath("../upload/test.docx");
            Response.TransmitFile(filename);
        }

        /// <summary>
        /// WriteFile实现下载
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        protected void btnWrite_Click(object sender, EventArgs e)
        {
            /*            using System.IO;                     */
            string fileName = "test.docx";//客户端保存的文件名
            string filePath = Server.MapPath("../upload/test.docx");//路径
            FileInfo fileInfo = new FileInfo(filePath);
            Response.Clear();
            Response.ClearContent();
            Response.ClearHeaders();
            Response.AddHeader("Content-Disposition", "attachment;filename=\"" + HttpUtility.UrlEncode(fileName, System.Text.Encoding.UTF8) + "\"");
            Response.AddHeader("Content-Length", fileInfo.Length.ToString());
            Response.AddHeader("Content-Transfer-Encoding", "binary");
            Response.ContentType = "application/octet-stream";
            Response.WriteFile(fileInfo.FullName);
            Response.Flush();
            Response.End();
        }

        /// <summary>
        /// WriteFile分块下载
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        protected void btnWriteFile_Click(object sender, EventArgs e)
        {
            string fileName = "test.docx";//客户端保存的文件名
            string filePath = Server.MapPath("../upload/test.docx");//路径
            System.IO.FileInfo fileInfo = new System.IO.FileInfo(filePath);
            if (fileInfo.Exists == true)
            {
                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];
                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
                Response.ContentType = "application/octet-stream";
                Response.AddHeader("Content-Disposition", "attachment; filename=" + HttpUtility.UrlEncode(fileName, System.Text.Encoding.UTF8));
                while (dataLengthToRead > 0 && Response.IsClientConnected)
                {
                    int lengthRead = iStream.Read(buffer, 0, Convert.ToInt32(ChunkSize)); //读取的大小
                    Response.OutputStream.Write(buffer, 0, lengthRead);
                    Response.Flush();
                    dataLengthToRead = dataLengthToRead - lengthRead;
                }
                Response.Close();
            }
        }

        /// <summary>
        /// 流放式下载
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        protected void btnFlow_Click(object sender, EventArgs e)
        {
            string fileName = "test.docx";//客户端保存的文件名
            string filePath = Server.MapPath("../upload/test.docx");//路径
            //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();
            Response.ContentType = "application/octet-stream";
            //通知浏览器下载文件而不是打开
            Response.AddHeader("Content-Disposition", "attachment; filename=" + HttpUtility.UrlEncode(fileName, System.Text.Encoding.UTF8));
            Response.BinaryWrite(bytes);
            Response.Flush();
            Response.End();
        }

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