I created a form which runs multiple background threads. I added another class which handles exceptions and errors if any. When the code runs, if an error occurs that should force the application to close can I just use Application.Exit()? Will that kill the background threads as well?
No, it will not. Application.Exit() will simply force the windows message pump to post a Quit message, which will terminate your application's main thread. However, the process itself will continue to run until the background threads complete.
Update: as commenters have correctly pointed out, if your thread's IsBackground property is set to True, terminating the main thread via Application.Exit() will shut down the process.
No. Thread termination is cooperative.
Related
I have a Windows Service that when it gets started It creates many backgroundworkers. and each backgroundworker monitors its own Queue in memory with the pending items to process.
When the process that created the backgroundworkers --windows service-- is stopped (either by request or because it crashed) are these background workers stoped or left orphan and still running ?
Do I need to write the code stop the backgropund workers when the windows service is about to be stopped ?
BackgroundWorkers use threads with IsBackground set to true, which means it will terminate when all non-background threads have terminated.
If your BackgroundWorker is going to do something where it should not be shut-down until it is completed, then it should set Thread.CurrentThread.IsBackground = false before it begins that crucial part, and set it back to true upon completion.
Edit: It's worth adding, that a process shutdown (unhandled exception, process killed through the task-manager or replacement, etc.) will end all threads. It's rather the reverse; ending all non-background threads will end the process (and take all background threads with them). It's this you need to worry about in terms of reacting to user input requesting the process terminate (service stop, last visible window closed, etc.)
In .NET applications and services when the main thread terminates all child background threads terminate as well.
Experimenting with the TcpClient and TcpListener class and for some reason when I have a couple of threads running and I close the form the process does not end but the form disappears.
I have to manually kill the process with the VS IDE or task manager.
Nothing in the form is still running from what I can tell when I close the program but the process does not end.. I insert breakpoints everywhere and even the console output says the threads exited.
Anyone know what's going on here?
The main thread of your application is waiting for the threads your spawned to finish. You can set the IsBackground property of your threads to true so they do not stop your process from terminating:
From MSDN:
A thread is either a background thread or a foreground thread.
Background threads are identical to foreground threads, except that
background threads do not prevent a process from terminating. Once all
foreground threads belonging to a process have terminated, the common
language runtime ends the process. Any remaining background threads
are stopped and do not complete.
After I close the main window of my program, the process is still running in the background.
How can I check what is the cause for this weird problem?
(I don't know which part of my program code is relevant)
First check that the value of your application's ShutdownMode property is equal to ShutdownMode.OnMainWindowClose -- if it is not, see if the actual value is preventing the app from closing.
If this does not solve the problem, then you have one or more non-background threads still running after the main window closes, preventing the process from shutting down. Break into the debugger and see how many threads are still alive and what they are doing; this will lead you to a solution.
To see the Thread that is currently running and stopping your application from termination just press "Break All" at the Visual Studio and see where the cursor stops.
Note: you can force application to terminate by calling Environment.Exit();
Another reason could be that someone set the Application.ShutdownMode to OnExplicitShutdown.
One possibility is that you create threads which are not set to background or you're calling code that does that; that may keep your process "alive" even after you shut down your main thread.
Make sure that you terminate all of your threads before you exit or you set their IsBackground property to true.
We have an application written in .net, c#, winforms. We noticed that sometimes when closing the application, the process remains.
I'm not sure how I can reproduce that behavior, so I'm looking for some clues as to why the application wouldn't exit.
The application uses a bit of background threads. Thread pools. Wondering if that could be the cause. Anything else could have this effect?
If you have thread's that have IsBackground property set to false that are alive after application is closed, they will remain
The application uses a bit of
background threads. Thread pools.
Wondering if that could be the cause.
Anything else could have this effect?
It most definitely could be the cause though I cannot be certain that it actually is. One way to test this hypothesis to make sure all threads that have been explicitly created are designated as background threads. This can be done by setting Thread.IsBackground = true which will allow the application to terminate if the main thread ends. If there is at least one thread for which IsBackground = false then the CLR keeps the host process running.
Its likely to be a thread left running. If you have a look at the process in task manager you can see when a thread starts, and how many are left running when it exits by adding the 'Threads' column from the view menu.
I would start by making sure you start and end on the same thread count.
Get Process Explorer and possibly Process Monitor and see what thread is left suspended or running.
If you are able to run in debug and you close the form, VS should not return to the normal code edit mode (it will still have the pause and stop buttons from debug active). You can then press Pause and check the Threads window to see where the call stacks are stuck for threads that are still active.
Strange issue. I kill the main thread, but when the program ends, it still processes the code after this.Close().
Any ideas on how to stop that?
MessageBox.Show("Servers overloaded. Exiting.");
this.Close();
//...other code that processes even after it closes...
Closing the window does not stop the thread.
You can use Environment.Exit to shutdown immediately.
Unlike ASP.Net's Response.End(), calling Close will not abort the thread.
You need to add return; after calling Close() to exit the method.
Why would it stop at Close()? It is still going to exit your method - most things like Close() are going to involve sending something to the windows message queue and having it processed. If you need to exit NOW, then perhaps Environment.FailFast...