How multiple events happen one by one by clicking a button? In an order.

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Hello

I am new in C#.

I want to make an basic app that shows two messages in a different text boxes by clicking one button. The second message most be appeared after two seconds.

I have tried the following code that dose not work. Indeed both of the messages are shown at once after two seconds.

What I have tried:

private void btn_play_Click(object sender, RoutedEventArgs e)
        {
                tb_hello.Text = "hello";
                Thread.Sleep(2000);
                tb_goodbye.Text = "goodbye";
        }

Posted 19-Jun-18 5:42am

bamshad1986

Updated 19-Jun-18 10:40am

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George Swan · Answer 1 · 2018-06-19T10:04:00

I would use the Task-based Asynchronous Pattern. await Task.Delay(2000) is an asynchronous 'wait' it does not block the UI thread. Note the async keyword in the method's signature.

C#

private async void btn_play_Click(object sender, RoutedEventArgs e)
       {
           tb_hello.Text = "hello";
           await Task.Delay(2000);
           tb_goodbye.Text = "goodbye";
       }

OriginalGriff · Answer 2 · 2018-06-19T05:48:00

Thread.Sleep suspends the current thread - which means that nothing at all happens until the period has elapsed. And that includes updates to display controls! Since you are updating UI controls, that code is running on the UI thread (or you'd get a cross threading exception) which means that Paint requests to update the actual display can't be honoured until the thread has finished sleeping, and the event handler exits.

Instead, show the first message then start a timer to replace it with the second.
In practice, I'd have a timer running full time, and use a counter that is reduced in the timer event handler to decide when to replace the message - it's a simpler solution that doesn't risk multiple timers running at the same time - they use resources that are scarce so that's a bad idea.

Gerry Schmitz · Answer 3 · 2018-06-19T10:41:00

Solution 3

Use one or more DispatcherTimers to update independent controls; particularly in WPF.

Since they run "on the UI thread", they are ideally suited for updating controls.

The DispatcherTimer - The complete WPF tutorial[^]

Posted 19-Jun-18 10:41am

Gerry Schmitz

How multiple events happen one by one by clicking a button? In an order.

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