如何使用Async/Await进行进度报告

Question

假设我有一个文件列表,我必须使用c#project中的ftp相关类复制到Web服务器.在这里我想使用Async/Await功能,并且还希望同时显示多个文件上传的多个进度条.每个进度条指示每个文件上载状态.所以指导我如何做到这一点.

当我们与后台工作人员合作完成这种工作时,这很容易,因为后台工作人员有进度变更事件.那么如何使用Async/Await处理这种情况.如果可能的话,用示例代码指导我.谢谢

Answer 1

从文章中获得进展的示例代码

public async Task<int> UploadPicturesAsync(List<Image> imageList, 
     IProgress<int> progress)
{
      int totalCount = imageList.Count;
      int processCount = await Task.Run<int>(() =>
      {
          int tempCount = 0;
          foreach (var image in imageList)
          {
              //await the processing and uploading logic here
              int processed = await UploadAndProcessAsync(image);
              if (progress != null)
              {
                  progress.Report((tempCount * 100 / totalCount));
              }
              tempCount++;
          }
          return tempCount;
      });
      return processCount;
}

private async void Start_Button_Click(object sender, RoutedEventArgs e)
{
    int uploads=await UploadPicturesAsync(GenerateTestImages(),
        new Progress<int>(percent => progressBar1.Value = percent));
}

如果您想独立报告每个文件,您将拥有IProgress的不同基本类型:

public async Task<int> UploadPicturesAsync(List<Image> imageList, 
     IProgress<int[]> progress)
{
      int totalCount = imageList.Count;
      var progressCount = Enumerable.Repeat(0, totalCount).ToArray(); 
      return Task.WhenAll( imageList.map( (image, index) =>                   
        UploadAndProcessAsync(image, (percent) => { 
          progressCount[index] = percent;
          progress?.Report(progressCount);  
        });              
      ));
}

private async void Start_Button_Click(object sender, RoutedEventArgs e)
{
    int uploads=await UploadPicturesAsync(GenerateTestImages(),
        new Progress<int[]>(percents => ... do something ...));
}