使用Tasks实现BackgroundWorker的RunWorkerCompleted答案

【问题标题】：Implementing BackgroundWorker's RunWorkerCompleted using Tasks使用Tasks实现BackgroundWorker的RunWorkerCompleted
【发布时间】：2011-05-24 15:00:07
【问题描述】：

我有一个 WPF MVVM 应用程序。在其中一个 ViewModel 中，我有以下内容：

this.GoCommand = new RelayCommand(() =>
{
    var scheduler = TaskScheduler.FromCurrentSynchronizationContext();

    Task.Factory.StartNew(() =>
        {
            for (int i = 0; i < 100; ++i)
            {
                this.Progress = i + 1;
                Thread.Sleep(30);
            }
        }).ContinueWith(task =>
            {
                // should act like RunWorkerCompleted
                this.DoSecondTask();
            },
            scheduler
        );
});

private void DoSecondTask()
{ 
    Task.Factory.StartNew(() =>
        {
            for (int i = 0; i < 100; ++i)
            {
                // repeated task for simplicity
                this.Progress = i + 1;
                Thread.Sleep(30);
            }
        }).ContinueWith(task =>
            {
                this.Status = "Done.";
            }
        );
}

当我单击绑定到 GoCommand 的按钮时，我看到进度条从 1 移动到 100。但是，当 ContinueWith 执行 DoSecondTask 时，该任务在 UI 线程中运行。如何更改 DoSecondTask 函数以在新线程（或 UI 线程之外）中运行第二个 for 循环？

【问题讨论】：

标签： .net c#-4.0 backgroundworker task

【解决方案1】：

我在this 答案中找到了解决方案。有趣的是，这不起作用：

private void DoSecondTask()
{ 
    Task.Factory.StartNew(_ =>
        {
            for (int i = 0; i < 100; ++i)
            {
                // repeated task for simplicity
                this.Progress = i + 1;
                Thread.Sleep(30);
            }
        }, TaskScheduler.Default).ContinueWith(task =>
            {
                this.Status = "Done.";
            }
        );
}

但这确实：

private void DoSecondTask()
{ 
    Task.Factory.StartNew(() =>
        {
            for (int i = 0; i < 100; ++i)
            {
                // repeated task for simplicity
                this.Progress = i + 1;
                Thread.Sleep(30);
            }
        }, CancellationToken.None, TaskCreationOptions.None, TaskScheduler.Default).ContinueWith(task =>
            {
                this.Status = "Done.";
            }
        );
}

【讨论】：