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  • C#实现文件下载的几种方式

    先把有问题的代码贴出来吧,

    using System;
    using System.Data;
    using System.Configuration;
    using System.Collections;
    using System.Web;
    using System.Web.Security;
    using System.Web.UI;
    using System.Web.UI.WebControls;
    using System.Web.UI.WebControls.WebParts;
    using System.Web.UI.HtmlControls;
    using System.IO;

    namespace infoPlatClient.NetDisk
    {
        public partial class downLoad : Com.DRPENG.Common.WebStruct.BaseForm
        {

            /// <summary>
            /// 取得要下载文件的路径
            /// </summary>
            private string fileRpath
            {
                get
                {
                    return Request["fileRpath"] == null ? "" : Request["fileRpath"];
                }
            }
            /// <summary>
            /// 取得要下载文件的名称
            /// </summary>
          
            protected void Page_Load(object sender, EventArgs e)
            {
                    if (!IsPostBack)
                    this.DownloadFile();
            }
            public void DownloadFile()
            {

                    Response.ClearHeaders();
                    Response.Clear();
                    Response.Expires = 0;
                    Response.Buffer =true;
                    Response.AddHeader("Accept-Language", "zh-tw");
                    string name = System.IO.Path.GetFileName(fileRpath);
                    System.IO.FileStream files = new FileStream(fileRpath, FileMode.Open, FileAccess.Read, FileShare.Read);
                    byte[] byteFile=null;
                    if (files.Length == 0)
                    {
                        byteFile=new byte[1];
                    }
                    else
                    {
                        byteFile = new byte[files.Length];
                    }
                    files.Read(byteFile, 0, (int)byteFile.Length);
                    files.Close();
                
                    Response.AddHeader("Content-Disposition", "attachment;filename=" + HttpUtility.UrlEncode(name, System.Text.Encoding.UTF8));
                    Response.ContentType = "application/octet-stream;charset=gbk";
                    Response.BinaryWrite(byteFile);
                    Response.End();
                 
            }
        }
    }

     之前一直用这种下载方式,可是有一次用户上传了一个700Mb的文件时报内存溢出的问题,分析了一下原因,用户的内存只有256M,而下载文件时要创建内存流,导致了内存溢出。

    解决方案:1>WriteFile分块下载,就是每次下载指定数量的多件;

                 2>通过超链接的方式;

                 lblDownLoad.Text = "<a href='" + drv["VPath"].ToString() + "'>下载</a>"

    下面是四种实现文件下载的方式:

    using System;
    using System.Data;
    using System.Configuration;
    using System.Web;
    using System.Web.Security;
    using System.Web.UI;
    using System.Web.UI.WebControls;
    using System.Web.UI.WebControls.WebParts;
    using System.Web.UI.HtmlControls;
    using System.IO;

    public partial class _Default : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {

        }

        //TransmitFile实现下载
        protected void Button1_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";
            Response.AddHeader("Content-Disposition", "attachment;filename=z.zip");
            string filename = Server.MapPath("DownLoad/z.zip");
            Response.TransmitFile(filename);
        }

        //WriteFile实现下载
        protected void Button2_Click(object sender, EventArgs e)
        {
            /*
             using System.IO;
            
             */

            string fileName ="asd.txt";//客户端保存的文件名
            string filePath=Server.MapPath("DownLoad/aaa.txt");//路径

            FileInfo fileInfo = new FileInfo(filePath);
            Response.Clear();
            Response.ClearContent();
            Response.ClearHeaders();
            Response.AddHeader("Content-Disposition", "attachment;filename=" + fileName);
            Response.AddHeader("Content-Length", fileInfo.Length.ToString());
            Response.AddHeader("Content-Transfer-Encoding", "binary");
            Response.ContentType = "application/octet-stream";
            Response.ContentEncoding = System.Text.Encoding.GetEncoding("gb2312");
            Response.WriteFile(fileInfo.FullName);
            Response.Flush();
            Response.End();
        }

        //WriteFile分块下载
        protected void Button3_Click(object sender, EventArgs e)
        {

            string fileName = "aaa.txt";//客户端保存的文件名
            string filePath = Server.MapPath("DownLoad/aaa.txt");//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));
                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();
            }
        }

        //流方式下载
        protected void Button4_Click(object sender, EventArgs e)
        {
            string fileName = "aaa.txt";//客户端保存的文件名
            string filePath = Server.MapPath("DownLoad/aaa.txt");//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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  • 原文地址:https://www.cnblogs.com/zhangzt/p/1623426.html
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