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# 项目中的 ftp 相关类将其复制到 Web 服务器。在这里，我想使用 Async/Await 功能，并且还想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的上传状态。所以请指导我如何做到这一点。

当我们与后台工作人员一起做这种工作时，这很容易，因为后台工作人员有进度更改事件。那么如何使用 Async/Await 来处理这种情况。如果可能的话，用示例代码指导我。谢谢

Answer 1

来自article的进度示例代码

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，您将有不同的 IProgress 基本类型：

public Task 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 ...));
}