stream流写到MemoryStream内存流引发得问题

采用httphandler去中转访问认证服务器。以下代码实现得是从认证远程服务器上下载资源到本地客户端。但实际连接到远程服务器上，下载文件所花费得时间非常长。大家分析下代码？看看程序所执行得时间花费在哪里，并减少这个时间花费。我认为该程序所花费太多时间，是发生在stream流写到内存流上。谢谢。讨论讨论。

页面上调用方法：

<a href="/aklib.aspx?fn=文件完整路径" target="_blank">文件名</a>

code:

  public class AutoDownload : IHttpHandler
    {

        #region IHttpHandler Members

        public bool IsReusable
        {
            get { return false; }
        }

        public void ProcessRequest(HttpContext context)
        {
            try
            {
                string fileName = SoFContext.Current.GetStringInQs("fn", string.Empty);
                string siteUrl= System.Configuration.ConfigurationManager.AppSettings["SiteUrl"].ToString();
                string user = System.Configuration.ConfigurationManager.AppSettings["FtpUser"].ToString();
                string passWord = System.Configuration.ConfigurationManager.AppSettings["FtpPassWord"].ToString();
                
                string filePath = string.Empty;
                 filePath = siteUrl+ fileName;
                
                string file = Path.GetFileName(filePath);

                HttpContext.Current.Response.Buffer = true;
                HttpContext.Current.Response.Charset = "utf-8";
                HttpContext.Current.Response.ContentEncoding = Encoding.UTF8;
                HttpContext.Current.Response.Clear();
                HttpContext.Current.Response.ContentType = "application/octet-stream";
                HttpContext.Current.Response.AppendHeader("Content-Disposition", "attachment; filename=" + HttpUtility.UrlEncode(file, Encoding.UTF8));
   
             HttpWebRequest httpWebRequest;
                httpWebRequest = (HttpWebRequest)HttpWebRequest.Create(filePath);

                NetworkCredential credential;
                if (!string.IsNullOrEmpty(user) && !string.IsNullOrEmpty(passWord))
                {
                    credential = new NetworkCredential(user, passWord);
                    httpWebRequest.Credentials = credential;
                }
                
                using (HttpWebResponse httpWebResponse = (HttpWebResponse)httpWebRequest.GetResponse())
                {
                    using (Stream responseStream = httpWebResponse.GetResponseStream())
                    {

                        byte[] arrayByte;
                        byte[] buffer = new byte[4096];
                        using (MemoryStream stmMemory = new MemoryStream())
                        {

                           int count = 0;
                            do
                            {
                                count = responseStream.Read(buffer, 0, buffer.Length);
                                stmMemory.Write(buffer, 0, count);

                            } while (count != 0);
                            
                            arrayByte = stmMemory.ToArray();

                            HttpContext.Current.Response.AppendHeader("Content-Length", arrayByte.Length.ToString());
                            HttpContext.Current.Response.BinaryWrite(arrayByte);

                            HttpContext.Current.Response.Flush();
                            HttpContext.Current.ApplicationInstance.CompleteRequest();
                        }



                    }
                }
            }
            catch (Exception ex)
            {
                System.Diagnostics.Debug.Fail(ex.Message);
                System.Diagnostics.Debug.Fail(ex.StackTrace);

            }
        }

HttpHandler有时使用并不是拥有很的性能。
考虑流量大的问题：建议使用异步的HttpHandler(具体参考MSDN做法)
那你做的方法：确
你的 HttpWebRequest是同步的, 如果文件大+并发高了 结果你自己知道！
另外你通过这种方式下载，相当于下了2次！ 你首先下载了一次到服务器内存，然后再把内存的东西发给用户.
实是拿内存进行了中转，所以花费一些时间。