文件流下载方法

/// <summary>
        /// 用流的方式下载文件
        /// </summary>
        /// <param name="filepath_name">文件路径及文件名</param>
        public static void FileDownLoad(string filepath_name)
        {
            System.IO.Stream iStream = null;

            //以10K为单位缓存:
            byte[] buffer = new Byte[10000];

            int length;

            long dataToRead;

            // 制定文件路径.
            string filepath = filepath_name;

            //  得到文件名.
            string filename = System.IO.Path.GetFileName(filepath);

            try
            {
                // 打开文件.
                iStream = new System.IO.FileStream(filepath, System.IO.FileMode.Open,
                            System.IO.FileAccess.Read, System.IO.FileShare.Read);


                // 得到文件大小:
                dataToRead = iStream.Length;

                System.Web.HttpContext.Current.Response.ContentType = "application/octet-stream";
                System.Web.HttpContext.Current.Response.AddHeader("Content-Disposition", "attachment; filename=" + filename);

                while (dataToRead > 0)
                {
                    //保证客户端连接
                    if (System.Web.HttpContext.Current.Response.IsClientConnected)
                    {
                        length = iStream.Read(buffer, 0, 10000);

                        System.Web.HttpContext.Current.Response.OutputStream.Write(buffer, 0, length);

                        System.Web.HttpContext.Current.Response.Flush();

                        buffer = new Byte[10000];
                        dataToRead = dataToRead - length;
                    }
                    else
                    {
                        //结束循环
                        dataToRead = -1;
                    }
                }
            }
            catch (Exception ex)
            {
                // 出错.
                System.Web.HttpContext.Current.Response.Write("Error : " + ex.Message);
            }
            finally
            {
                if (iStream != null)
                {
                    //关闭文件
                    iStream.Close();
                }
            }
        }