unity + WebClient显示下载速度，当前下载量，下载总量

            using (WebClient client = new WebClient()) {
                sw.Start();
                client.DownloadProgressChanged += new DownloadProgressChangedEventHandler(ProgressChanged);
                client.DownloadFileAsync(new System.Uri(url), currDownFile);
            }

private void ProgressChanged(object sender, DownloadProgressChangedEventArgs e) {
        //下载的总量
        PrecentData preData = new PrecentData();
        preData.total = string.Format("{0} MB / {1} MB", (e.BytesReceived / 1024d / 1024d).ToString("0.00"),  (e.TotalBytesToReceive / 1024d / 1024d).ToString("0.00"));
        preData.precent = (float)e.BytesReceived / (float)e.TotalBytesToReceive;



            string value = string.Format("{0} kb/s", (e.BytesReceived / 1024d / sw.Elapsed.TotalSeconds).ToString("0.00"));

        preData.speed = value;

        Loom.QueueOnMainThread((param) =>
        {
            NotificationCenter.Get().ObjDispatchEvent(KEventKey.m_evDownload, preData);
        }, null);

        
            NotiData data = new NotiData(NotiConst.UPDATE_PROGRESS, value);
            if (m_SyncEvent != null) m_SyncEvent(data);

            if (e.ProgressPercentage == 100 && e.BytesReceived == e.TotalBytesToReceive) {
                sw.Reset();

                data = new NotiData(NotiConst.UPDATE_DOWNLOAD, currDownFile);
                if (m_SyncEvent != null) m_SyncEvent(data);
            }
        }

string.Format("{0} MB / {1} MB", (e.BytesReceived / 1024d / 1024d).ToString("0.00"),  (e.TotalBytesToReceive / 1024d / 1024d).ToString("0.00"));

string.Format("{0} kb/s", (e.BytesReceived / 1024d / sw.Elapsed.TotalSeconds).ToString("0.00"));