C# 文件下载四方法

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)
    {
        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)
    {
        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();
    }
}