Argument exception null

Information this. CallState, string. Authority, resource, clientKey. ClientId, tokenCache! Count : "null", subjectType ; this. Error this. Example 7. File: PoisonTest. Equal new ExceptionDetails exception , poison. Example 8. File: ExceptionExtensionsTest. Equal outer. Message, outer. Example 9. File: SeriesDetailsTest. Empty ; Assert. Equal expected. Message, actual.

Example File: ResolveAppointmentsEventArgs. FirstOrDefault ; if movedItem! Remove movedItem ; this. File: ExceptionsHelperTests. AreEqual expected, ExceptionsHelper. File: ArgumentNullExceptionTests. AreEqual ex. IsTrue ex. Message, "Value cannot be null. File: EFAssembly. FAddIn" ; WzdUtils. GetServerPath WzdUtils. Remove path. File: p. RemoveSetting Umbraco. Format "ConfigurationManager. File: ConnectionExtensions. File: StatusLoggerTest. LogMessage messageToLog ; Assert. IsTrue resetEvent.

WaitOne TimeoutValue ; Assert. Public methods often begin with a series of tests to detect unacceptable null inputs, or similar mistakes. For example, the code calling one of your library functions might have been compiled with the NRT feature disabled. NET development tools commonly started enabling this in new projects. There are a couple of problems with this. First, it's verbose.

Depending on your code style preferences, you might be able to mitigate that by moving the throw onto the same line as the if , and losing the braces, but it's still a bit of a mess.

The second problem is that it's easy to make a particular mistake. I've made that mistake here: did you spot it? My second throw passes the wrong argument name. So if somebody passes a null for name , I'll throw an exception erroneously complaining that they passed a null id. This issue is slightly less bad than it was a few years ago, thanks to nameof : at least if I rename an argument by refactoring it, this sort of reference to its name will automatically pick up the change and if I rename it without using a refactoring, I'll get a compiler error where I used nameof with the old name.

But that doesn't help me if I referred to entirely the wrong argument. There's no doubt that this is more compact. And I find that the resulting layout makes it much easier to see at a glance which arguments I'm dealing with here although that's subjective, of course. There's also no longer any opportunity to make the mistake my first example made with the name argument: I can't check one argument for null , and then throw an exception that accidentally points the finger at a completely different argument.

This is impossible here because I only name each argument once. But how does this work? How is ThrowIfNull going to discover the argument name? I've passed it the value of the argument, but it's not obvious how, at runtime, it's going to determine the name to use when throwing an exception. And yet it works exactly how you'd hope. The ThrowIfNull helper is able to discover the argument name thanks to a new feature in C This type has been in the. Improve this answer. Yeah, it's not a matter of preference.

You might use [code contracts][1] to minimize the code overhead of ArgumentNullException : Contract. It still has the duplicate reference to x but that's the only drawback. If you are thinking "buy why is it correct? Pang 8, gold badges 82 82 silver badges bronze badges. Chris Marisic Chris Marisic I prefer the explicit exception, for these reasons: If the method has more than one SomeClass argument it gives you the opportunity to say which one it is everything else is available in the call stack.

What if you do something that may have a side effect before referencing x? Joel Coehoorn Joel Coehoorn k gold badges silver badges bronze badges. Andrew Hare Andrew Hare k 68 68 gold badges silver badges bronze badges.

If only C had the Null safe dereferncing operator then we would have something like x?. Anastasiosyal Hey, C does have this now, almost 4 years later! Yes, at long last, it's here! Happy days : — Anastasiosyal. AndyWarby AndyWarby 2 2 silver badges 3 3 bronze badges. Pretty interesting syntax! I'd prefer the parameter check with the explicit ArgumentNullException, too. Oliver Friedrich Oliver Friedrich 8, 7 7 gold badges 40 40 silver badges 48 48 bronze badges.

I suppose I should have spent more time reading the documentation on the constructor. NotNull x,"x","someMethod received a null x argument! NotNull y,"y","someMethod received a null y argument! Szymon Rozga Szymon Rozga How about the stacktrace in the exception? It would contain the Guard method NotNull, which is only noise, and might cause confusion. Is there some way of avoiding this? The better code readability outweights the little noise in the stacktrace imo.

ThrowIfNull x,"x","received a null x argument! Well it's a bit of extra work, but you can construct the stacktrace yourself and tell the stacktrace constructor to skip one frame so that the Guard.

NotNull gets excluded from the trace. You of course have to inherit from your desired exception type as well and override the Exception. StackTrace property.

Well anyway you decide if it's worth it or not - it's just code-candy. That is because Code Analysis won't know that Guard. NotNull is doing the check for null. Patrick Desjardins Patrick Desjardins k 82 82 gold badges silver badges bronze badges. Aaron Fischer Aaron Fischer I'll probably be downvoted for this, but I think completely different.

If it's optional, use default values if your language supports them or create an overload. Much cleaner than ugly exceptions. You don't know who might be calling your method some day in the future long after you changed jobs, or how many layers an object has passed through before reaching your method.

Relying on your method not receiving null is not a viable option as it's beyond your control. Throwing a meaningful exception is within your control. The less code, the better. For me, using argument checking brings benefit only when you need to fail fast. Otherwise, don't pass null.