c# - 将后台 worker 更新为异步等待

Question

这就是我目前使用后台工作程序将大量内容保存到文件的方式，同时向用户显示进度条并防止在保存过程中对 UI 进行任何更改。我想我已经掌握了基本特征。模态 ProgressWindow 显示一个进度条，仅此而已。如果必须的话，我将如何将其更改为 async-await 模式？

private ProgressForm ProgressWindow { get; set; }

/// <summary>On clicking save button, save stuff to file</summary>
void SaveButtonClick(object sender, EventArgs e)
{
  if (SaveFileDialog.ShowDialog() == DialogResult.OK)
  {
    if (!BackgroundWorker.IsBusy)
    {
      BackgroundWorker.RunWorkerAsync(SaveFileDialog.FileName);
      ProgressWindow= new ProgressForm();
      ProgressWindow.SetPercentageDone(0);
      ProgressWindow.ShowDialog(this);
    }
  }
}

/// <summary>Background worker task to save stuff to file</summary>
void BackgroundWorkerDoWork(object sender, DoWorkEventArgs e)
{
  string path= e.Argument as string;

  // open file

  for (int i=0; i < 100; i++)
  {
    // get some stuff from UI
    // save stuff to file
    BackgroundWorker.ReportProgress(i);
  }

  // close file
}

/// <summary>On background worker progress, report progress</summary>
void BackgroundWorkerProgressChanged(object sender, ProgressChangedEventArgs e)
{
  ProgressWindow.SetPercentageDone(e.ProgressPercentage);
}

/// <summary>On background worker finished, close progress form</summary>
void BackgroundWorkerRunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
  ProgressWindow.Close();
}

Answer 1

我有一个 blog series详细介绍了这一点。

简而言之，BackgroundWorker被 Task.Run 取代, 和 ReportProgress (和 friend )被替换为 IProgress<T> .

所以，一个简单的翻译应该是这样的:

async void SaveButtonClick(object sender, EventArgs e)
{
  if (SaveFileDialog.ShowDialog() == DialogResult.OK)
  {
    ProgressWindow = new ProgressForm();
    ProgressWindow.SetPercentageDone(0);
    var progress = new Progress<int>(ProgressWindow.SetPercentageDone);
    var task = SaveAndClose(SaveFileDialog.FileName, progress));
    ProgressWindow.ShowDialog(this);
    await task;
  }
}

async Task SaveAndClose(string path, IProgress<int> progress)
{
  await Task.Run(() => Save(path, progress));
  ProgressWindow.Close();
}

void Save(string path, IProgress<int> progress)
{
  // open file

  for (int i=0; i < 100; i++)
  {
    // get some stuff from UI
    // save stuff to file
    if (progress != null)
      progress.Report(i);
  }

  // close file
}

改进说明:

• 让后台线程进入 UI 通常不是一个好主意 (// get some stuff from UI)。如果您可以在 调用 Task.Run 之前从 UI 收集所有信息，它可能会更好。并将其传递给 Save方法。