Keyboard won't dismiss even after Focus change

Question

I am creating a Windows 8.1 app and after the user presses a button, a popup opens over most of the screen. There are several textboxes inside the popover.

I found

Answer 1

In UWP Windows 10 simple disable/enable doesn't work anymore. But this works:

            TextBox.IsEnabled = false;

            var t = new DispatcherTimer();
            t.Interval = new TimeSpan(0, 0, 1);
            t.Tick += (a, b) =>
            {
                t.Stop();
                TextBox.IsEnabled = true;
            };
            t.Start();

Find more elegant solution? Please share.