在UI上延迟调用+更新CountDown

Question

I want to delay loading data anywhere between 1 and 20 seconds. I also want to update the UI with the countdown to update like "Updating data in x..."

I can do Task.Delay, or DispatcherTimer or Aysnc/await but how do I update the UI with every second countdown ?

Sample to put my point across (it won't work for me since this is blocking UI thread).

private void Update()
    {
        var random = new Random();
        var counter = random.Next(1, 20);
        for (int i = counter; i > 0; i--)
        {
            UpdateCounter = i;// property bound to UI to update the countdown
            Thread.Sleep(1000); // 
        }
        // some function to update data...
    }

Answer 1

There are a lot of options how to do it. I implemented 2 of them. I would recommend second, but it depends on your needs.

    private void Update1()
    {
        Task.Factory.StartNew(() =>
            {
                var random = new Random();
                var counter = random.Next(1, 20);
                for (int i = counter; i > 0; i--)
                {
                    Dispatcher.Invoke(() => UpdateCounter = i);
                    Task.Delay(1000).Wait();
                }
                Dispatcher.Invoke(// some function to update data...);
            }
        );
    }

    private async Task Update2()
    {
        var random = new Random();
        var counter = random.Next(1, 20);
        for (int i = counter; i > 0; i--)
        {
            UpdateCounter = i;
            await Task.Delay(1000);
        }

        // some function to update data...
    }