We have different ways to kill a running C# program.
ctrl + C;
task bar then right click its icon, then select 'close' on the popup;
task manager, select the its executable name and then click end process;
console window, use kill command;
maybe more.
What I am asking here is how handle them in my C# program to guarantee my C# program exit gracefully when possible. I know how to trap ctrl + C, but don't the others. can you help me? thanks,
The best guarantee you have at code being run at exit is the finally statement.
Note though that your program will have to run in the try block when you use this mechanism.
I believe that the only time the block inside the finally is not executed are at:
A StackOverflowException;
Corrupted state exceptions (from .NET 4);
Forceful termination through the task manager (an unmanaged process kill);
Crash of the entire system (removing the power cable e.g.).
See Keep Your Code Running with the Reliability Features of the .NET Framework for an in depth analysis.
Scenario 2 basically calls Application.Exit(), which should amount to a graceful shutdown of all threads associated with your process. It also fires events you can use to perform any additional cleanup.
3 and 4 can be "trapped" by attaching a handler to the Application.ThreadException event of a WinForms app. This event is fired when any exception is about to be thrown out of the program to be handled by the runtime (which will terminate your assembly's execution and clean the sandbox). However, at this point there's very little you should do other than write something to the Event log or clean up any statics, like an IoC container or repository, and even that's problematic because if one of those objects caused the exception, you could very easily throw another exception in trying to deal with the last one.
Basically, if your user is using "kill" or "End Process" to close your app, there's something VERY wrong and you should probably address the underlying reason why a user would be doing that, before trying to gracefully capture such termination behaviors.
Cannot trap. You cannot avoid killing of a program. But you can always subscribe to kill. Just imaging how you can trap when people pull the power plug...
.NET 2.0
Subscribe to the AppDomain.CurrentDomain.ProcessExit event
.NET 3.5
Application.Exit Event
Useful links
AppDomain.CurrentDomain.ProcessExit and cleanup
How to detect when application terminates?
How to detect when main thread terminates?
Related
I've developed a program (winforms application, not a service) in C# that runs on a windows server.
The program starts multiple times based on requests from outside the server.
From time to time I see that the program is "Suspended" for an unknown reason. I think it is related to a lack of resources, but not sure.
How can I prevent windows from suspending my program?
Update
To be clear, I know that the program crash and it is OK. What I'm asking is not how to improve performance \ prevent the crash, but how to remove the process from the process list \ prevent this suspended status?
Depends in your hardware/software configuration, it's hard to know where is your bottleneck.
I recommend instead to do Multi-thread/task app where you're able to control threads and asign priority, resources, stop, resume, abort, etc...
use on command console to start and check if happends the same but with the parameter high:
start /HIGH <ProgramPath>
Read more how to change priority on executables
Task Scheduler on windows servers MSDN -> Priority
(It's only an opinion, start digging about others solutions.)
You must set the ServiceBase.CanPauseAndContinue Property to False in the constructor of the service before it is started.
NOTE the side effect is:
If CanPauseAndContinue is false, the SCM will not pass Pause or
Continue requests to the service, so the OnPause and OnContinue
methods will not be called even if they are implemented. In the SCM,
the Pause and Continue controls are disabled when CanPauseAndContinue
is false.
For more information see this Microsoft Doc
There are multiple methods of keeping an app awake.
One method would be to request a deferral and then only mark that deferral complete when you are done.
First you need a deferral object that will remain in scope of your process
SuspendingDeferral deferral
Then you need to override OnSuspending
async protected void OnSuspending(object sender, SuspendingEventArgs args)
{
deferral = args.SuspendingOperation.GetDeferral();
await SuspensionManager.SaveAsync();
}
Then you need to mark the deferral complete when your process is done doing whatever it was doing
if (deferral is not null) { deferral.Complete(); }
Full details can be found in the Microsoft docs
For discussion of other methods see this thread:
How to Disable UWP App Suspension?
Technically the process is suspended but if you look at the memory consumption of 32K you can tell it was not suspended. Your process did crash with an unhandled exception which in turn triggers Windows Error Reporting to take a memory dump.
This involves some kernel magic which keeps a process handle in the kernel (System process) alive. It is not a big deal or memory leak since the process did already terminate. Only the PEB (Process Environment Block) the 32K which includes mostly command line, loaded dlls and environment variables are still there.
I would not worry about suspended processes but why your process did crash with an unhandled exception. This could even be a feature to make programers aware that their process did crash by looking at a looong list of suspended processes in Task Manager ;-).
Since it is a .NET Application you will find a generic error messages that a process did crash in the Application event log and a .NET Runtime logged error message with more exception details.
Perhaps that is already enough to keep you going to fix your issue. If not you can configure WER to create a full memory dump via a registry setting (https://learn.microsoft.com/en-us/windows/win32/wer/collecting-user-mode-dumps). Now you have for each "suspended" process a full memory dump you can load into Visual Studio to look further what was the issue.
To further check who holds your process handle still open you can use handle e.g. ProcessHacker (the better Process Explorer) https://processhacker.sourceforge.io/nightly.php
If something else is happening you can see with this tool who is holding any outstanding handles to your process open. But I strongly suspect it is the Windows Kernel.
I have a process that I would like to be able to cleanly shut down from an external process. That is, I would like to give it a chance to clean up it's resources (save it's data etc.) before it dies.
Process.CloseMainWindow appears to be the ordinary way to go, except the process in question doesn't have any windows and I don't want to immediately call Process.Kill because I want to give it chance to clean up first (and a kill process command can't be intercepted by the target process).
So what is the best way to allow my process to be shut cleanly from another process?
I have control over both processes. The process to be shut does have a message loop (Application.Run()) so I would think there would be some message I could post through there.
I have read the msdn article on terminating processes and this article about closing processes cleanly however both mention methods that seem quite sophisticated despite the simplicity of what I am trying to achieve. Given that I have control over both processes I am hoping there's something a bit simpler that can be implemented cleanly in C#. Is there one?
The process to close is not a service, so can't do service stop.
I'm not sure if a .NET message loop supports thread messages, or only window messages. If it supports thread messages, then the terminating app can use PostThreadMessage() to post a WM_QUIT message (or a custom message that the message loop can look for) to the main thread of the target process so it can stop its message loop and exit the app.
Otherwise, have the target app create a named kernel event object using EventWaitHandle and then wait on the event, either by calling EventWaitHandle.WaitOne() in a manual thread, or calling ThreadPool.RegisterWaitForSingleObject() to use a system-provided thread pool. When the event is signaled, you can notify the main thread to exit the app. The terminating app can then open the event object by name using EventWaitHandle.OpenExisting(), and then signal the event with EventWaitHandle.Set().
I have an application that I am writting that communicates with a third-party program through a COM connection. I was tasked to strengthen the resilency of our application, in order to do that I wait until the third-party application is ready. I do this by waiting until the return value on a method that returns true only when the third-party application has been fully loaded.
In an effort to avoid the condition where the application crashes during this procedure, and my application just sits there waiting throwing COM errors( caught of course ) I was wondering if the Exited event on the Process itself, is guaranteed to always happen?
I am more then willing to provide additional details when its possible. I am also for the time being limited to .NET Framework 2.0 with this current build.
It depends on the sort of crash - some crashes leave the "process" in memory (for example just stuck in some never-ending loop OR that COM object opened some modal error dialog and waits for user)... these cases are not covered by any method mentioned in your description...
In my experience to be really resilient you need a combination:
hook the Exited event (if you started the application via Process) OR find the process ID and monitor that
catch any exceptions from that COM object
implement a timeout + abort logic for calls to that COM object/application
"monitor" the COM object/app
I usually start a separate thread before calling such a COM object... that thread monitors the COM object/application for example if it open any window it is not supposed or memory consumption goes through the roof when it is not supposed to etc. - the things monitored and the reaction to each of them is rather specific to that COM object/application...
I have a console application written in C#/.NET that I want to run from a script (nant). If an exception occurs in the console application, I would like nant to continue, but in Windows Vista there is a popup that searches for solutions and asks for debug etc.
I would like to avoid the popup with "program stopped working" when an exception happens in the console application. How can I control this from C#/.NET?
(A similar question addresses the issue for the C language, but I would like a solution for C#/.NET.)
(To clarify: I would like the exception to be passed to nant, but without the popup.)
The JIT debugger popup occurs when there's an unhandled exception. That is, an exception tunnels all the way up the stack to the root of any thread in the runtime.
To avoid this, you can handle the AppDomain.CurrentDomain.UnhandledException event and just call Environment.Exit(1) to exit gracefully.
This will handle all exceptions on all threads within your AppDomain. Unless you're doing anything special, your app probably only has one AppDomain, so putting this in your public static void Main method should suffice:
AppDomain.CurrentDomain.UnhandledException += (sender, args) =>
{
Console.Error.WriteLine("Unhandled exception: " + args.ExceptionObject);
Environment.Exit(1);
};
You should probably use the NAnt logger to write out the error in this case too (can't recall the API for this offhand though.)
You can also disable JIT debugging on the machine. I would only recommend this in certain circumstances such as for a dedicated build server.
Under Windows Vista you can disable this dialog for your programms.
Disable the "Problem Reports and Solutions feature". You find it under Control Panel-->Problem Reports and Solutions-->Change Settings-->Advanced Settings-->Turn off for my programs, problem reporting
Just catch the exception and log/ignore it.
The popup appears due to an unhandled exception. To avoid that make sure your main method captures all exceptions and turn them into some other useful piece of info you can pick up. Just ignoring the exception is not recommended.
Btw remember that exceptions are per thread, so if your application spawns threads or uses thread pool threads, you need a handler for these too.
Usually this only happens when your app doesnt handle an exception. If you wrap your whole console app in a try/catch bblock, and just pass back a fail code, then you will avoid this.
Sometimes, a windows application will stop working if you are using a System.Timers.Timer.
To fix this, change System.Timers.Timer by System.Windows.Forms.Timer
Greetings
We have a SmartClient built in C# that stubornly remains open when the PC its running on is being restarted. This halts the restart process unless the user first closes the SmartClient or there is some other manual intervention.
This is causing problems when the infrastructure team remotely installs new software that requires a machine reboot.
Any ideas for getting the SmartClient app to recognize the shutdown/restart event from Windows and gracefully kill itself?
UPDATE:
This is a highly threaded application with multiple gui threads. yes, multiple gui threads. Its really a consolidation of many project that in and of themselves could be standalone applications - all of which are launched and managed from a single exe that centralizes those management methods and keeps track of those threads. I don't believe using background threads is an option.
OK, if you have access to the app, you can handle the SessionEnded event.
...
Microsoft.Win32.SystemEvents.SessionEnded +=new
Microsoft.Win32.SessionEndedEventHandler(shutdownHandler);
...
private void shutdownHandler(object sender, Microsoft.Win32.SessionEndedEventArgs e) {
// Do stuff
}
It must be a thread that continues to run preventing your application to close. If you are using threading an easy fix would be to set it to background.
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.
http://msdn.microsoft.com/en-us/library/system.threading.thread.isbackground.aspx
When a user is logging off or Windows is being shut down, WM_QUERYENDSESSION message is sent to all top-level windows. See MSDN documentation here.
The default behavior of a WinForm application in response to this message is to trigger the FormClosing event with CloseReason == WindowsShutDown or others. The event handler though can choose to be stubborn and refuse to shut the app down, thus keeping the system running.
Check FormClosing handlers of your applications. Maybe there is something in there. I've seen this kind of stuff a couple of times.
Or maybe the .Net app is ignoring close or quit messages on purpose?
Background threads was a quick and dirty solution, best solution is to use synchronization objects (ManualResetEvent, Mutex or something else) to stop the other threads;
Or else keep track of all your opened windows and sent WM_CLOSE message when main app closes.
You have to give more information about how do you start those GUI applications. maybe you start one thread for each application and call Application.Run(new Form1()); ?
You may also look into creating a AppDomain for each GUI Application
Normally a .Net app would respond correctly- at least, that's the 'out of the box' behavior. If it's not, there could be a number of things going on. My best guess without knowing anything more about your program is that you have a long-running process going in the main UI thread that's preventing the app from responding to window messages.