平行的.Foreach和Task冲突

我在并行执行中上传图像到云

// Make a TaskFactory that will use the UI thread's context
var uiFactory = new TaskFactory(TaskScheduler.FromCurrentSynchronizationContext());
Parallel.ForEach(FinalFileNames,
    new ParallelOptions { MaxDegreeOfParallelism = 4 },
    path =>
    {
         count++;
         /* Calculate percentage of upload done */
         double iPercentDone = (int)(((float)count / iTotalFiles) * 100);
        // Send the progress report to the UI thread.
        uiFactory.StartNew(() =>
        UploadProgress.Value = iPercentDone;
        LblProgress.Content = count.ToString(CultureInfo.InvariantCulture)
                               + " file(s) uploaded from " + iTotalFiles +
                     " file(s)";
                        }
       });

我面临的问题是，当我这样做时，UI被阻塞了。原因似乎是在同一个线程中工作。

如果我把这个平行。"Task.Factory"中的每一个。New"，表示它正在进行异步调用，这不是我的要求。

请让我知道，我怎么能解决UI块问题，以及不使呼叫异步。