Try that!

[BernieTheBernie]

Bernie was tasked with adding some new functionality, and thus investigated the code base to find the best extension points. He stumbled upon code "trying" quite a lot:

private async void Timer_Elapsed(object _sender, ElapsedEventArgs _e)
{
	try
	{
		await Task.Run(() => DoSomething());
	}
	finally
	{
		m_Timer.Start();
	}
}

...

private void DoSomething()
{
	try
	{
		...
		ISomething something = FindSomething(...);
		...
		Run(...);
	}
	catch (Exception ex)
	{
		Logger.LogException(Name, ex);
	}
}

...

private ISomething FindSomething(...)
{
	switch (...)
	{
		case ...:
			...
			return new Something(...);
		default:
			throw new SpecialException("Blah blah blah.");
	}
}

...

private void Run(...)
{
	string exceptionMessages = "";

	Task taskMain = Task.Run(() => ...);

	try
	{
		taskMain.Wait();
	}
	catch (AggregateException ex)
	{
		foreach (Exception innerException in ex.InnerExceptions)
		{
			exceptionMessages += innerException.Message + " / " + innerException.StackTrace + " # ";
		}
	}

	if (taskMain.Exception?.InnerException != null)
	{
		exceptionMessages += taskMain.Exception.InnerException.Message + " / " + taskMain.Exception.InnerException.StackTrace + " # ";
	}
	if (!string.IsNullOrEmpty(exceptionMessages))
	{
		throw new SpecialException($"Error(s) in special task: {exceptionMessages}");
	}
}

The DoSomething method will never throw any exception: all exceptions raised therein are also caught and logged there.
Hence it is useful to enclose the Task in the Timer event handler with a try..finally, isn't it?

The Run method runs a task and catches its exceptions. It takes a lot of care to collect all the exception messages and stack traces, feeds them into a new exception, which unspecifically gets caught in DoSomething, and logged (and the Logger has some functionality to take care of AggregateExceptions, InnerExceptions, StackTraces, and exception messages, too - with better formatting, of course).

By the way, what would happen if some exception entered that Timer event handler? Well, there is a finally: that should re-enable the timer. Without a catch, that's very useful when such a ThreadException just crashed the application.

Oh sanctissimi Wilhelmus, Theodorus et Fredericus. Deliberate me a ho malo. Amen.

[Tsaukpaetra]

Odd, apparently you've posted seven things, but I'm privy to only two of them....

[ben_lubar]

@tsaukpaetra said in Try that!:

Odd, apparently you've posted seven things, but I'm privy to only two of them....

Looks like an import bug.

[BernieTheBernie]

@tsaukpaetra Well, I don't see them either... We're here on the Daily WTF, aren't we?

[boomzilla]

@berniethebernie I don't see them either, which is tightly related to why @ben_lubar says it's an import bug.

[Tsaukpaetra]

@boomzilla said in Try that!:

@berniethebernie I don't see them either, which is tightly related to why @ben_lubar says it's an import bug.

I can only assume they're posts that had NULL characters in them....

[TheCPUWizard]

@berniethebernie said in Try that!:

The DoSomething method will never throw any exception: all exceptions raised therein are also caught and logged there.
Hence it is useful to enclose the Task in the Timer event handler with a try..finally, isn't it?

It may be true that "DoSomething" will never throw, but that does not mean the same thing about Task.Run(...) :)