下载文件时不要全部读入内存(C#)

FileStream stream = new FileStream(path, FileMode.Open); 
   Response.ContentType = "application/octet-stream";
   Response.AppendHeader("Content-Disposition", "attachment;filename=" + HttpUtility.UrlEncode(filename,System.Text.Encoding.UTF8));
   
   //开始下载文件，注意这里下载必须1024*1024个字节的读，不能一次读入内存，否则服务器必死
   try
   {
    int nowLength = 0;
    int maxLengthPerPackage = 1024*1024;
    byte[] by;
    for(;nowLength < stream.Length;)
    {
     by = new byte[maxLengthPerPackage];
     int canReadLength = stream.Read(by, 0, by.Length); // 读取文件内容
     //this.SocketSendText(by,false,0,canReadLength);
     Response.BinaryWrite(by);
     nowLength += maxLengthPerPackage;
    }
   }
   finally
   {
    if (stream != null)
    {
     stream.Close();
    }
   }