传送文件的问题(客户下载文件)

[WM_JAWIN]

有没有人做下防盗连的.帮我看看这个代码.
我在测试时现在Transporting有时不会减.表现为:状态显示503.
且Development Sever的CPU占用率为100%
测试时一般情况,都能正常下载,且下载完成之后Development Sever的CPU占用为零.
当下载完成之后 Development Sever的cpu占用率为100%时,再次下载就会出现503.
跟踪代码可以发现503是因为(Transporting >= 1)

为什么CPU会一直占用呢?

//App_Code
class ft{
static int Transporting=0;
        /// <summary>
        /// 文件传送
        /// </summary>
        /// <param name="file">要传送的文件</param>
        /// <param name="s">开始点</param>
        /// <param name="e">结束点</param>
        private static void TransmitToClient(string file,int s,int e )
        {
            if (s >= e && e!=-1)
                return;
            FileStream fStm = new FileStream(file, FileMode.Open, FileAccess.Read);
            byte[] bin = new byte[1024];
            HttpResponse Response = HttpContext.Current.Response;
            if (Transporting >= 1)
            {//超过下载人数限制,限一人同时下载
                Response.StatusCode =503;
                Response.End();
            } 
            Transporting++;

            System.IO.Stream oStm=Response.OutputStream;
            oStm.Flush();
            
            if(s>0)
                fStm.Seek(s, SeekOrigin.Begin);
            if (e == -1)
                e =(int) fStm.Length;

            int c = 0;
            
            try { 
                do
                {
                    if (!Response.IsClientConnected)
                        break;
                    c = fStm.Read(bin, 0, 1024);
                    oStm.Write(bin, 0, c);
                    oStm.Flush();
                    s += c;
                } while (c > 0 || e <= s);
            }
            catch (Exception)
            {/*nothing to do*/
            } 
  
            Transporting--;
            if(Transporting<0)
                Transporting=0;

            fStm.Close();
            fStm.Dispose();
            fStm = null;
            oStm = null;
        }
}