项目:Lesson1_DownLoad
Default.aspx:
    <form id=”form1″ runat=”server”>
    <div>
        下载的方法列举:<br />
        <asp:Button ID=”Button1″ runat=”server” Text=”DownLoad” OnClick=”Button1_Click” Font-Bold=”True”/>
    </div>
    </form>

    Default.aspx.cs
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; //added
public partial class _Default : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {

    }
    //下载
    protected void Button1_Click(object sender, EventArgs e)
    {
        //方法一:TransmitFile实现下载
        /*
            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(“~/z.zip”);
        //Response.TransmitFile(filename);

        //方法二:WriteFile实现下载 
        //string fileName = “asd.txt”;//客户端保存的文件名
        //string filePath = Server.MapPath(“~/zhangq.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();

        //方法三:WriteFile分块下载 
        //string fileName = “zhangq.txt”;//客户端保存的文件名
        //string filePath = Server.MapPath(“~/zhangq.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();
        //}

        //方法四:流方式下载
        //string fileName = “aaa.txt”;//客户端保存的文件名
        //string filePath = Server.MapPath(“~/zhangq.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();

        //方法五:动态产生一个文本文件zhangqing.txt,文件内容是第三个参数的值.
        //DownloadFile(this, “zhangqing”, “zhangqing!”);

        //方法六:动态产生一个文本文件zhangqing.txt,文件内容是服务器端已存在的文件zhangq.txt的内容
        string filePath = Server.MapPath(“~/zhangq.txt”);//路径
        DownloadFileByFilePath(this, “zhangqing”, filePath);
    }

    //方法五:
    public void DownloadFile(System.Web.UI.Page WebForm, String FileNameWhenUserDownload, String FileBody)
    {

        WebForm.Response.ClearHeaders();
        WebForm.Response.Clear();
        WebForm.Response.Expires = 0;
        WebForm.Response.Buffer = true;
        WebForm.Response.AddHeader(“Accept-Language”, “zh-tw”);
        //\’文件名称
        WebForm.Response.AddHeader(“content-disposition”, “attachment; filename=\'” + System.Web.HttpUtility.UrlEncode(FileNameWhenUserDownload, System.Text.Encoding.UTF8) + “\'”);
        WebForm.Response.ContentType = “Application/octet-stream”;
        //\’文件内容
        WebForm.Response.Write(FileBody);//———–
        WebForm.Response.End();
    }

    public void DownloadFileByFilePath(System.Web.UI.Page WebForm, String FileNameWhenUserDownload, String FilePath)
    {
        WebForm.Response.ClearHeaders();
        WebForm.Response.Clear();
        WebForm.Response.Expires = 0;
        WebForm.Response.Buffer = true;
        WebForm.Response.AddHeader(“Accept-Language”, “zh-tw”);
        //文件名称
        WebForm.Response.AddHeader(“content-disposition”, “attachment; filename=\'” + System.Web.HttpUtility.UrlEncode(FileNameWhenUserDownload, System.Text.Encoding.UTF8) + “\'”);
        WebForm.Response.ContentType = “Application/octet-stream”;
        //文件内容
        WebForm.Response.Write(System.IO.File.ReadAllBytes(FilePath));//———
        WebForm.Response.End();
    }
}

参考:http://hi.baidu.com/dreamyear/blog/item/6c50202a031a1b305343c12b.html