asp.net 用流的方式下载文件

//以下代码根据别人文章和自己整理
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.IO;
namespace WebApplication1
{
public partial class DownfFile : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{

}
/// <summary>
/// WriteFile下载
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
protected void Button1_Click(object sender, EventArgs e)
{
string name ="DreamweaverCS3简体中文免激活绿色版.rar";
string path =Server.MapPath("DreamweaverCS3简体中文免激活绿色版.rar");
FileInfo fileinfo = new FileInfo(path);
long size = fileinfo.Length;
Response.Clear();
Response.ContentType = "application/octet-stream";
Response.AppendHeader("Content-Disposition", "attachment;filename=" + name);
Response.AppendHeader("Content-Length", size.ToString());
Response.AppendHeader("Content-Transfer-Encoding", "binary");
Response.ContentEncoding = System.Text.Encoding.UTF8;//GetEncoding("gb2312");
Response.WriteFile(path,0,size);
Response.Flush();
Response.End();
}
/// <summary>
/// 使用OutputStream.Write分块下载文件
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>

protected void Button2_Click(object sender, EventArgs e)
{
string fileName = HttpContext.Current.Server.UrlEncode("DreamweaverCS3简体中文免激活绿色版.rar");
string filePath = HttpContext.Current.Server.MapPath("DreamweaverCS3简体中文免激活绿色版.rar");
//如果要写类的话用HttpResponse h