asp.net 几种文件下载方式比较

来源：互联网发布：淘宝电商运营试题编辑：程序博客网时间：2024/04/30 20:22

/*
     * asp.net 几种文件下载方式比较
     *
     * 方法1、HttpResponse.TransmitFile
     * 方法2、HttpResponse.WriteFile
     * 方法3、HttpResponse.BinaryWrite
     * 方法4、HttpResponse.Redirect
     *
     * 方法1与方法2
     *      相同点：都是通过文件的相对或绝对路径下载文件；
     *      不同点：方法2是一次性将文件读入内存，然后输出给客户端；
     *              方法1不在内存中缓冲文件。
     *
     *      因此，对于大文件或用户数多的下载，方法1不会对于服务器内存的占用将远远低于方法2；
     *      这正是方法1的最大优势，
     *      但方法1也有一个局限：does not work with UNC-share file paths.     *
     *      UNC (Universal Naming Convention) / 通用命名规则，也叫通用命名规范、通用命名约定。
     *      它符合 \servername\sharename 格式
     *      也就是说方法1无法下载网络共享磁盘的文件
     *
     *      例如:
     *      if (filePath.StartsWith(@"\\"))
     *          context.Response.WriteFile(filePath, false);
     *      else
     *          context.Response.TransmitFile(filePath);
     *
     * 方法3
     *      方法3主要是将已有的btye[] 型对象输出到客户端；
     *      如果要下载的文件位于数据库等存储介质，那么，读入内存时一般可放于DataTable等对象中，
     *      这时就可以直接HttpResponse.BinaryWrite((byte[])dt.Rows[0]["fileContent"])输出
     *
     * 方法4
     *      方法4主要是通过文件的相对路径下载文件；     *
     *
     *
     * 以上四个方法，如果下载一个汉字命名且字数超过20个字的文件
     * 方法1不会有问题；
     * 使用其它三个方法下载后，如果客户端在提示框中点“打开”将报错，提示文件名过长。
     *
     */ 以下是测试用到的 download.aspx 及 download.cs的代码：

download.aspx

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="download.aspx.cs" Inherits="download" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
</head>
<body>
    <form id="form1" runat="server">
    <div> <asp:Button ID="btnDownloadByRedirect" runat="server"
            Text="using Response.Redirect()" onclick="btnDownloadByRedirect_Click"
            />
        <asp:Button ID="btnDownloadByTransmitFile" runat="server" Text="using Response.TransmitFile()"
            onclick="btnDownloadByTransmitFile_Click" />
        <asp:Button ID="btnDownloadByWriteFile" runat="server" Text="using Response.WriteFile()"
            OnClick="btnDownloadByWriteFile_Click" />
        <asp:Button ID="btnDownloadByBinaryWrite" runat="server" Text="using Response.BinaryWrite()"
            OnClick="btnDownloadByBinaryWrite_Click"  />
    </div>
    </form>
</body>
</html>

download.cs

using System;

using System.Collections.Generic;

using System.Linq;

using System.Web;

using System.Web.UI;

using System.Web.UI.WebControls;

using System.IO;

using System.Text;

public partial class download : System.Web.UI.Page

{

protected void Page_Load(object sender, EventArgs e)

{

//System.Threading.Thread.Sleep(5000);

//Download(HttpContext.Current.Response);

}

protected void btnDownloadByRedirect_Click(object sender, EventArgs e)

{

Download(HttpContext.Current.Response);

}

protected void btnDownloadByTransmitFile_Click(object sender, EventArgs e)

{

Download(HttpContext.Current.Response, DownloadMethod.TransmitFile);

}

protected void btnDownloadByWriteFile_Click(object sender, EventArgs e)

{

Download(HttpContext.Current.Response, DownloadMethod.WriteFile);

}

protected void btnDownloadByBinaryWrite_Click(object sender, EventArgs e)

{

Download(HttpContext.Current.Response, DownloadMethod.BinaryWrite);

}

private FileInfo info = null;

private enum DownloadMethod

{

WriteFile,

BinaryWrite,

TransmitFile

}

private bool PrepareFile()

{

string applicationPath = HttpContext.Current.Request.PhysicalApplicationPath;

string lastCharacter = applicationPath.Substring(applicationPath.Length - 1);

if (!lastCharacter.Equals("\\"))

{

applicationPath = applicationPath + "\\";

}

info = new FileInfo(applicationPath + "Files\\测试文件测试文件测试文件测试文件测试文件测.xls");

return info.Exists;

}

private byte[] GetFileByte()

{

return File.ReadAllBytes(info.FullName);

}

private long GetFileLength()

{

return info.Length;

}

private void Download(HttpResponse response)

{

if (PrepareFile())

{

response.Redirect("Files/" + info.Name, true);

}

private void Download(HttpResponse response, DownloadMethod method)

{

if (PrepareFile())

{

response.Clear();

response.ClearHeaders();

response.Buffer = false;

string displayName = HttpUtility.UrlEncode(Encoding.UTF8.GetBytes(info.Name));

response.AppendHeader("Content-Disposition", "attachment;filename=" + displayName);

response.ContentType = "application/octet-stream";

switch (method)

{

case DownloadMethod.WriteFile:

//response.WriteFile(info.FullName);

response.TransmitFile("Files/" + info.Name);

break;

case DownloadMethod.BinaryWrite:

response.BinaryWrite(GetFileByte());

break;

case DownloadMethod.TransmitFile:

//response.TransmitFile(info.FullName);

response.TransmitFile("Files/" + info.Name);

break;

}

response.Flush();

response.End();

}