Why does the UI still freeze even though I use Task in C# WPF?-CodePudding

I have a C# WPF project I want to use a task to display a spinner (loader) without freezing the UI so that the long process is finished.

What I need: I want to show a loading to the user during a heavy operation

What have I done: Well, I have a spinner that is hidden and when heavy operations start, I show that spinner ,But the UI freezes again!

CS:

 private void Button1_Click(object sender, RoutedEventArgs e)
        {
            //Showing the loader
            Task.Factory.StartNew(async () =>
            {
                await Dispatcher.InvokeAsync(() =>
                {
                    Spinner.Visibility = Visibility.Visible;

                });
            });

            //Simulation Long Process
            var TheRsult = dbms.Database.SqlQuery<object>("WAITFOR DELAY '00:00:04' SELECT GETDATE()").FirstOrDefault();
            Thread.Sleep(500);
            for (int i = 0; i < 1000; i  )
            {
                Console.Write(i);
            }
        }

My Full Source Code : https://filebin.net/n354bf7ngyspoy5f

Please guide me regarding this issue, thank you

CodePudding user response：

You're "Simulation Long Process" on main thread (put a breakpoint at Thread.Sleep(500); and the IDE will tell you that you're in MainThread)..

You can change your code to something like this

private async void Button1_Click(object sender, RoutedEventArgs e)
{
    // Showing the loader
    Spinner.Visibility = Visibility.Visible;
    
    // or: await Task.Run(() =>     
    await Task.Factory.StartNew(() =>
    {
        // Simulation Long Process
        var TheRsult = dbms.Database.SqlQuery<object>("WAITFOR DELAY '00:00:04' SELECT GETDATE()").FirstOrDefault();
        Thread.Sleep(500);
        for (int i = 0; i < 1000; i  )
        {
            Console.Write(i);
        }
    });
    
    Spinner.Visibility = Visibility.Hidden;
}

CodePudding user response：

Task has nothing to do with threading.

And as you can plainly see, there's absolutely nothing running on a separate thread in your code. The first part shows your spinner on your main thread (Dispatcher.InvokeAsync), and the second part runs straight in the button handler, on the main thread.