c# wpf keep ui response not working (c# thread )

https://docs.microsoft.com/en-us/windows/uwp/debug-test-perf/keep-the-ui-thread-responsive

Above url says that don't put UI things with main working function.

// Perform background work here. // Don't directly access UI elements from this method.

The key point is let sub function be called inside:

await Task.Run(() => 'your function working long');

If you mix up main thread and ui thread, below error happens.

the calling thread cannot access this object

UI part code should be seprated from 'async work thread'. Otherwise you have error.

Read related article thoroughly:

https://stackoverflow.com/questions/9732709/the-calling-thread-cannot-access-this-object-because-a-different-thread-owns-it

https://www.codeproject.com/Questions/553275/C-23plus-2fplusWPFplusplus-3aplusThepluscallingplu

Below code will not work for showing spinner

            uiBefore();

            ConnectionChanged();

            uiAfter();

Below code works

            uiBefore();

            await Task.Run(() =>

            {

                ConnectionChanged();

            });

            uiAfter();

        private void uiBefore()

        {

            faSpinner.Visibility = Visibility.Visible;

        }

        private void uiAfter()

        {

            faSpinner.Visibility = Visibility.Collapsed;

        }

It seems funciton inside await Task.Run() doesn't have to be async function. Only the parent function needs to be async. Below code works.