如何触发方法在 x 秒后运行？

Question

I am working on a C# Windows Forms application where I need the method to pause for 30 seconds until it continues on to the next line of code. I have tried Thread.Sleep() which wasn't suitable for this application and I've understood that I should use some sort of timer instead. I have searched a lot but I can't figure out how to implement timers.

My code is below and could anyone show me how I should implement the timer. I have made a comment on where I want the method to pause.

private void start_Vid_Click(object sender, EventArgs e)
{
    if (video.State != StateFlags.Running)
    {
        viewport.Visible = true;
        video.Play();
    }

    //Here I want to wait 30 seconds until the next line of code is triggered

    viewport.Visible = false;
    viewport2.Visible = true;
    pictureBox1.Visible = true;
    start_Webc(); 
    video2.Play();
}

Answer 1

If your app is a .Net 4.5 application, then it's somewhat easier to use Task :

private async void start_Vid_Click(object sender, EventArgs e)
{
    if (video.State != StateFlags.Running)
    {
        viewport.Visible = true;
        video.Play();
    }

    await Task.Delay(TimeSpan.FromSeconds(30));

    viewport.Visible = false;
    viewport2.Visible = true;
    pictureBox1.Visible = true;
    start_Webc();
    video2.Play();
}

Answer 2

Task.Delay is not available on .NET 4.0, but you can start task, which will just sleep for 30 seconds, and later you can continue on UI thread again:

Task.Factory.StartNew(() => Thread.Sleep(30 * 1000))
            .ContinueWith((t) =>
    {
         viewport.Visible = false;
         viewport2.Visible = true;
         pictureBox1.Visible = true;
         start_Webc(); 
         video2.Play();
    }, TaskScheduler.FromCurrentSynchronizationContext());

Answer 3

System.Threading.Tasks.Task.Delay( 60 * 1000 ).ContinueWith( (_) => StartVoid() );

Answer 4

At class level define an instance of Timer (There are a few classes like this - for a winforms app you should use System.Windows.Forms.Timer )

static System.Windows.Forms.Timer myTimer = new System.Windows.Forms.Timer();

Then in your method add lines to handle its tick and start it:

private void start_Vid_Click(object sender, EventArgs e)
{
    if (video.State != StateFlags.Running)
    {
        viewport.Visible = true;
        video.Play();
    }

    myTimer.Tick += (o,ea) => {    
        viewport.Visible = false;
        viewport2.Visible = true;
        pictureBox1.Visible = true;
        start_Webc(); 
        video2.Play();
        myTimer.Stop();
    }
    myTimer.Interval = 5000; // 5 seconds
    myTimer.Start();
}

Answer 5

反应性扩展也有一种方法：

Observable.Return("Delayed").Delay(TimeSpan.FromSeconds(30)).Subscribe(val => Console.WriteLine("Executing delayed"));

Answer 6

We can do that using Task from

System.Threading.Tasks.Task.Factory.StartNew(() =>
        {
            Thread.Sleep(5000);
            this.Invoke(new Action(() => 
                Method1()));
        });

Answer 7

case WPF..

• WPF extension:

public static partial class WpfUtils
{
    public static void RunAfter(double seconds, Action action)
    {
        if (Application.Current.Dispatcher == null)
            return;
        var myTimer = new DispatcherTimer(
            DispatcherPriority.Normal,
            Application.Current.Dispatcher)
        {
            Interval = TimeSpan.FromSeconds(seconds)
        };
        myTimer.Tick += (_, _) =>
        {
            action?.Invoke();
            myTimer.Stop();
        };
        myTimer.Start();
    }
}

• Usage:

WpfUtils.RunAfter(3, () =>
{
    // some code
    Console.WriteLine("Running after 3 seconds");
});

Note that this code will run on the UI thread.. on the other hand, if you go with methods from Task class, the delayed code will run on a background thread.

• Showcase:

Task.Delay(6 * 1000).ContinueWith(_ =>
{
    // this will run in a background-thread
    var b = Thread.CurrentThread.IsBackground;
    Debug.Assert(b);
    Console.WriteLine("3");
});
var timer = new DispatcherTimer
{
    Interval = TimeSpan.FromSeconds(3)
};
timer.Tick += (_, _) =>
{
    // this will run in the UI-thread
    var b = Thread.CurrentThread.IsBackground;
    Debug.Assert(!b);
    Console.WriteLine("2");
    timer.Stop();
};
timer.Start();

Console.WriteLine("1");

// output
// 1
// 2
// 3