Q:

Label in WPF application not updating

I have the following code:
label1.content = "Start";
bool a = executeLongTask();
label1.content = "Done";

For some reason the label only gets updated to "Done" after the executeLongTask() method is completed. It completely skips displaying the "Start" message.
Why is the label not being set to "Start" when the application is running and how would I make it update to "Start" first without using multiple threads?
The executeLongTask() method by the way calls a PowerShell script and awaits it output before proceeding onto label1.content = "Done";

A:

For some reason the label only gets updated to "Done" after the executeLongTask() method is completed. It completely skips displaying the "Start" message.

That's because the UI thread needs to return to its main loop in order to process WM_PAINT updates. When you set the label the first time, WPF makes a note that it should redraw the label when it returns to the message processing loop. Then the UI is kept busy in the executeLongTask method, and then the label is set the second time, and WPF again makes a note that it should redraw the label. When you return control to the UI message loop, it finally gets a chance to actually do the redraw and update what you see on the screen.

how would I make it update to "Start" first without using multiple threads?

The easiest solution is to use multiple threads. Example:
label1.content = "Start";
bool a = await Task.Run(() => executeLongTask());
label1.content = "Done";

Alternatively, you could rewrite executeLongTask to act asynchronously, and then you wouldn't need a separate thread:
label1.content = "Start";
bool a = await executeLongTaskAsync();
label1.content = "Done";

