Multithreading: how to update UI to indicate progress

Question

I've been working on the same project now since Christmas 2008. I've been asked to take it from a Console Application (which just prints out trace statements), to a full Windows App. Sure, that's fine. The only thing is there are parts of the App that can take several minutes to almost an hour to run. I need to multithread it to show the user status, or errors. But I have no idea where to begin.

I've aready built a little UI in WPF. It's very basic, but I'd like to expand it as I need to. The app works by selecting a source, choosing a destination, and clicking start. I would like a listbox to update as the process goes along. Much in the same way SQL Server Installs, each step has a green check mark by its name as it completes.

How does a newbie start multithreading? What libraries should I check out? Any advice would be greatly appreciated.

p.s. I'm currently reading about this library, http://www.codeplex.com/smartthreadpool

@Martin: Here is how my app is constructed:

1. Engine: Runs all major components in pre-defined order
2. Excel: Library I wrote to wrap COM to open/read/close/save Workbooks
3. Library: Library which understands different types of workbook formats (5 total)
4. Business Classes: Classes I've written to translate Excel data and prep it for Access
5. Db Library: A Library I've written which uses ADO.NET to read in Access data
6. AppSettings: you get the idea
7. Serialier: Save data in-case of app crash

I use everything from LINQ to ADO.NET to get data, transform it, and then output it.

My main requirement is that I want to update my UI to indicate progress

@Frank: What happens if something in the Background Worker throws an Exception (handled or otherwise)? How does my application recieve notice?

@Eric Lippert: Yes, I'm investigating that right now. Before I complicate things.

Let me know if you need more info. Currently I've running this application from a Unit Test, so I guess callig it a Console Application isn't true. I use Resharper to do this. I'm the only person right now who uses the app, but I'd like a more attractive interface

Answer 1

I don't think you specify the version of the CLR you are using, but you might check out the "BackgroundWorker" control. It is a simple way to implemented multiple threads.

The best part, is that it is a part of the CLR 2.0 and up

Update in response to your update: If you want to be able to update the progress in the UI -- for example in a progress bar -- the background worker is perfect. It uses an event that I think is called: ProgressChanged to report the status. It is very elegant. Also, keep in mind that you can have as many instances that you need and can execute all the instances at the same time (if needed).

In response to your question: You could easily setup an example project and test for your question. I did find the following, here (under remarks, 2nd paragraph from the caution):

If the operation raises an exception that your code does not handle, the BackgroundWorker catches the exception and passes it into the RunWorkerCompleted event handler, where it is exposed as the Error property of System.ComponentModel..::.RunWorkerCompletedEventArgs.

Answer 2

Threading in C# from Joseph Albahari is quite good.