高分求助：c#的下载代码里如何控制线程的个数和每个用户的下载流量

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;
using system.threading;

/// <summary>
/// filedownload 的摘要说明
/// </summary>
public class filedownload
{
    /// <summary>
    /// 输出硬盘文件，提供下载 支持大文件、续传、速度限制、资源占用小
    /// </summary>
    /// <param name="_request">page.request对象</param>
    /// <param name="_response">page.response对象</param>
    /// <param name="_filename">下载文件名</param>
    /// <param name="_fullpath">带文件名下载路径</param>
    /// <param name="_speed">每秒允许下载的字节数</param>
    /// <returns>返回是否成功</returns>
    public static bool responsefile（httprequest _request, httpresponse _response, string _filename, string _fullpath, long _speed)
    {
        try
        {
            filestream myfile = new filestream（_fullpath, filemode.open, fileaccess.read, fileshare.readwrite);
            binaryreader br = new binaryreader（myfile);
            try
            {
                _response.addheader（"accept-ranges", "bytes");
                _response.buffer = false;
                long filelength = myfile.length;
                long startbytes = 0;

                int pack = 10240; //10k bytes
                //int sleep = 200;   //每秒5次   即5*10k bytes每秒
                int sleep = （int)math.floor（（decimal)1000 * pack / _speed) + 1;
                if （_request.headers["range"] != null)
                {
                    _response.statuscode = 206;
                    string[] range = _request.headers["range"].split（new char[] { '=', '-' });
                    startbytes = convert.toint64（range[1]);
                }
                _response.addheader（"content-length", （filelength - startbytes).tostring（));
                if （startbytes != 0)
                {
                    _response.addheader（"content-range", string.format（" bytes {0}-{1}/{2}", startbytes, filelength - 1, filelength));
                }
                _response.addheader（"connection", "keep-alive");
                _response.contenttype = "application/octet-stream";
                _response.addheader（"content-disposition", "attachment;filename=" + httputility.urlencode（_filename, system.text.encoding.utf8));

                br.basestream.seek（startbytes, seekorigin.begin);
                int maxcount = （int)math.floor（（decimal)（filelength - startbytes) / pack) + 1;

                for （int i = 0; i < maxcount; i++)
                {
                    if （_response.isclientconnected)
                    {
                        _response.binarywrite（br.readbytes（pack));
                        thread.sleep（sleep);
                    }
                    else
                    {
                        i = maxcount;
                    }
                }
            }
            catch
            {
                return false;
            }
            finally
            {
                br.close（);
                myfile.close（);
            }
        }
        catch
        {
            return false;
        }
        return true;
    }

}