c# - 所有任务完成后我的用户界面得到更新

Question

查看我下面的代码并告诉我有什么问题，当所有任务完成时我的 UI 正在更新，但根据代码，当我的例程被任务调用时，它应该更新标签值。在我的代码中更改什么。

例如，当 DoSomething1 被调用时，label3 需要更新并反射(reflect)在用户之前。

private void button1_Click(object sender, EventArgs e)
{
    TaskScheduler uiScheduler = TaskScheduler.FromCurrentSynchronizationContext();
    var token = Task.Factory.CancellationToken;

    var tasks = new[]
    {
        Task.Factory.StartNew( DoSomething1,token,TaskCreationOptions.None, uiScheduler),
        Task.Factory.StartNew(DoSomething2,token,TaskCreationOptions.None, uiScheduler),
        Task.Factory.StartNew(DoSomething3,token,TaskCreationOptions.None, uiScheduler)
    };
    Task.WaitAll(tasks);
    //var things = Task.WhenAll(tasks);

    int x=0;
}

public void DoSomething1()
{
    //this.label3.BeginInvoke(new Action(() =>
    //{
    //    this.label3.Text = "DoSomething1 -- " + System.Threading.Thread.CurrentThread.ManagedThreadId;
    //}));
    this.label3.Text = "DoSomething1 -- " + System.Threading.Thread.CurrentThread.ManagedThreadId;
    System.Threading.Thread.Sleep(1000);
}

public void DoSomething2()
{
    //this.label4.BeginInvoke(new Action(() =>
    //{
    //    this.label4.Text = "DoSomething2 -- " + System.Threading.Thread.CurrentThread.ManagedThreadId;
    //}));
    this.label4.Text = "DoSomething2 -- " + System.Threading.Thread.CurrentThread.ManagedThreadId;
    System.Threading.Thread.Sleep(1000);
}

public void DoSomething3()
{
    //this.label5.BeginInvoke(new Action(() =>
    //{
    //    this.label5.Text = "DoSomething3 -- " + System.Threading.Thread.CurrentThread.ManagedThreadId;
    //}));
    this.label5.Text = "DoSomething3 -- " + System.Threading.Thread.CurrentThread.ManagedThreadId;
    System.Threading.Thread.Sleep(1000);
}

Answer 1

The other answer就目前而言是正确的。使用 FromCurrentSynchronizationContext() 会导致正在使用的调度程序始终使用当前线程来运行任务。 IE。用户界面线程。任务应该使用 Task.Run() 运行并且没有特定的调度程序(它将默认为线程池调度程序)。 BeginInvoke() 是正确访问 Label 对象的一个​​选项。

但是，在我看来，最好修复所有代码，使其在当前的 async/await 范例中更加惯用。例如:

private async void button1_Click(object sender, EventArgs e)
{
    // Your original example didn't show how you used this value,
    // so I don't have anything in this example that uses it. But you
    // would probably want to pass it to the "DoSomething..." methods
    // so that those methods can then pass the token to whatever async
    // operation they are actually doing. See additional comment below.
    var token = Task.Factory.CancellationToken;

    var tasks = new[]
    {
        DoSomething1(),
        DoSomething2(),
        DoSomething3()
    };
    await Task.WhenAll(tasks);

    int x=0;
}

public async Task void DoSomething1()
{
    this.label3.Text = "DoSomething1 -- " + System.Threading.Thread.CurrentThread.ManagedThreadId;
    // replace with `Task.Run()` or whatever already-asynchronous
    // operation you need/want. Likewise in the other methods.
    // Don't forget to pass the CancellationToken to these methods,
    // and then on to whatever tasks you actually are running.
    await Task.Delay(1000);
}

public async Task DoSomething2()
{
    this.label4.Text = "DoSomething2 -- " + System.Threading.Thread.CurrentThread.ManagedThreadId;
    await Task.Delay(1000);
}

public async Task DoSomething3()
{
    this.label5.Text = "DoSomething3 -- " + System.Threading.Thread.CurrentThread.ManagedThreadId;
    await Task.Delay(1000);
}