How to put delay before doing an operation in WPF

问题:

I tried to use the below code to make a 2 second delay before navigating to the next window. But the thread is invoking first and the textblock gets displayed for a microsecond and landed into the next page. I heard a dispatcher would do that.

Here is my snippet:

tbkLabel.Text = "two mins delay";
Thread.Sleep(2000);
Page2 _page2 = new Page2();
_page2.Show();

回答1:

The call to Thread.Sleep is blocking the UI thread. You need to wait asynchronously.

Method 1: use a DispatcherTimer

tbkLabel.Text = "two seconds delay";

var timer = new DispatcherTimer { Interval = TimeSpan.FromSeconds(2) };
timer.Start();
timer.Tick += (sender, args) =>
    {
        timer.Stop();
        var page = new Page2();
        page.Show();
    };

Method 2: use Task.Delay

tbkLabel.Text = "two seconds delay";

Task.Delay(2000).ContinueWith(_ => 
   { 
     var page = new Page2();
     page.Show();
   }
);

Method 3: The .NET 4.5 way, use async/await

// we need to add the async keyword to the method signature
public async void TheEnclosingMethod()
{
    tbkLabel.Text = "two seconds delay";

    await Task.Delay(2000);
    var page = new Page2();
    page.Show();
}