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:

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。