void md_OnEvent(object sender, DownloadArgs e)
        {
            try
            {
                switch (e.status)
                {
                case DownloadStatus.CompleteOne_Success:
                    ResponseParser rp = new ResponseParser();
                    ret = rp.GetResultXElement(e.data);
                    break;

                case DownloadStatus.CompleteAll_Success:
                    this.waitHandle.Set();
                    break;

                case DownloadStatus.CompleteAll_Error:
                    this.ex = new Exception(e.data);
                    this.waitHandle.Set();
                    break;

                default:
                    break;
                }
            }
            catch (Exception ex)
            {
                this.ex = ex;
            }
        }