How to asynchronously wait for x seconds and execute something then?

You can start an asynchronous task that performs your action:

Task.Factory.StartNew(()=>
{
    Thread.Sleep(5000);
    form.Invoke(new Action(()=>DoSomething()));
});

[EDIT]

To pass the interval in you simply have to store it in a variable:

int interval = 5000;
Task.Factory.StartNew(()=>
{
    Thread.Sleep(interval);
    form.Invoke(new Action(()=>DoSomething()));
});

[/EDIT]

You can wait UI thread the way you want it to work.

Task.Factory.StartNew(async() =>
{
    await Task.Delay(2000);

    // it only works in WPF
    Application.Current.Dispatcher.Invoke(() =>
    {
        // Do something on the UI thread.
    });
});

if you're using .Net Framework 4.5 or higher version, you can use Task.Run instead of Task.Factory.StartNew just like below.

int millisecondsDelay = 2000;

Task.Run(async() =>
{
    await Task.Delay(millisecondsDelay);

    // it only works in WPF
    Application.Current.Dispatcher.Invoke(() =>
    {
        // Do something on the UI thread.
    });
});

Have you tried

public static Task Delay(
    int millisecondsDelay
)

You can use like this:

await Task.Delay(5000);

reference: https://msdn.microsoft.com/en-us/library/hh194873(v=vs.110).aspx

(transcribed from Ben as comment)

just use System.Windows.Forms.Timer. Set the timer for 5 seconds, and handle the Tick event. When the event fires, do the thing.

...and disable the timer (IsEnabled=false) before doing your work in oder to suppress a second.

The Tick event may be executed on another thread that cannot modify your gui, you can catch this:

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

    private void StartAsyncTimedWork()
    {
        myTimer.Interval = 5000;
        myTimer.Tick += new EventHandler(myTimer_Tick);
        myTimer.Start();
    }

    private void myTimer_Tick(object sender, EventArgs e)
    {
        if (this.InvokeRequired)
        {
            /* Not on UI thread, reenter there... */
            this.BeginInvoke(new EventHandler(myTimer_Tick), sender, e);
        }
        else
        {
            lock (myTimer)
            {
                /* only work when this is no reentry while we are already working */
                if (this.myTimer.Enabled)
                {
                    this.myTimer.Stop();
                    this.doMyDelayedWork();
                    this.myTimer.Start(); /* optionally restart for periodic work */
                }
            }
        }
    }

---

Just for completeness: with async/await, one can delay execute something very easy (one shot, never repeat the invocation):

private async Task delayedWork()
{
    await Task.Delay(5000);
    this.doMyDelayedWork();
}

//This could be a button click event handler or the like */
private void StartAsyncTimedWork()
{
    Task ignoredAwaitableResult = this.delayedWork();
}

For more, see "async and await" in MSDN.