Text Message in a window while waiting for an event to occur

Question

I am trying to display a message like 'Please Wait...' in a window, while an event is taking place. I don't want a message box, because that requires a button press. I just want this to be message that I can display and erase.

I've tried adding a TextBlock in the window (WPF), with an initial value of "", then changing the value right before I start the event (in C#), but the message doesn't appear until after the event happens. The event I am doing is creating a window with removable drives, which takes a short amount of time. I think the message appears when the ShowDialog for the new window happens. How do I redraw/refresh the current window with the TexBlock before my event starts so that I get the 'Please Wait...' message immediately? Or, is there a different way of doing this?

Sutton

Sam Hobbs · Answer

Then the concept of threads/tasks will be easy for you to understand. You understand the concept of events and interrupts. You know that processors execute code continuously until the code either polls/checks for something or there is an interrupt of some type. In your situation the main thread that owns the UI must execute to the extent that it is able to update the window but the other processing prevents that. It is not done automatically instantaneously at the moment you change the text for the window. Correspondingly and this is more important when the user does something in the UI the thread is not able to process that if it is doing something else so the user might click a button but nothing happens. If you have an opportunity to understand how Windows works at the API/SDK level you will learn about the message loop and how that is used to process events. In Windows UI events do not interrupt the UI thread; the thread that owns the window. Something else that you will quickly learn is that windows are not thread-safe; many (most) things cannot be done to a window by any thread other than its owner.

Sutton Mehaffey · Answer

Thanks. I'll read up on it and figure out what to do. I've done embedded programming for over 20 years but haven't messed much with Windows programming. Sutton

Sam Hobbs · Answer

Hopefully your question plus much more will be answered in the article and other articles. I actually answered the question though; so since you do not understand it will be better for you to get the explanation from existing resources such as the article. I said that you need another thread so you can keep the UI responsive. Computers can do many things at the same time or at least appear to. It requires however that developers do something so that computers know how to keep thing separate. I am being vague because  create a thread to do the other work so that your UI remains responsive  is more specific but I need to explain that in another way. If you want the UI to be able to do things such as put the text in itself (the form; the UI) at the same time that your program does other things then you need to make those two separate threads. Windows cannot do both at the same time; you the developer must make it possible for Windows to do both. Some programmers use shortcuts such as using a DoEvents function to avoid creating another thread but once you learn about threads you will have no problem doing that many more times in the future and you will be able to use the same knowledge many more times in the future. It is something you need to know how to do as a programmer; the concept is relevant to other operating systems too such as Linux which includes Android and WebOS.

Sutton Mehaffey · Answer

Thanks. I'll read up on it. Why would I have to create a background thread if what I want to do occurs in the foreground and in the current window? Sutton

Sam Hobbs · Answer

Certainly there is a better way. I assume you are not creating a background thread and that is what you need to do. You need to create a thread to do the other work so that your UI remains responsive. Have a look at Multithreading in WPF Part I and Multithreading in WPF: Part II . There are probably other articles to help you so have a look at the WPF articles.