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I'm working on a large project where, even with 10s of 1000s of automated tests and 100% code coverage, we're getting a ridiculous number of errors. About 95% of errors we get are NullReferenceExceptions.
Is there any way to enforce null-checking at compile time?
Barring that, is there any way to automagically enforce null-checking in unit tests without having to write the tests for null cases myself?
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One way of avoiding returning null is using the Null Object pattern. Basically you return a special case object that implements the expected interface. Instead of returning null you can implement some kind of default behavior for the object. Returning a null object can be considered as returning a neutral value.
A null indicates that a variable doesn't point to any object and holds no value. You can use a basic 'if' statement to check a null in a piece of code. Null is commonly used to denote or verify the non-existence of something.
It is a good idea to check for null explicitly because: You can catch the error earlier. You can provide a more descriptive error message.
A foreign key may not be null when it is part of a composite primary key in the child table.
You should look into Code Contracts. The static checker is only available for the higher-end VS editions, but that's basically what you're after.
There are plenty of resources online, and <plug> you can also read a prerelease version of the chapter on Code Contracts from the 2nd edition of C# in Depth - download chapter 15 for free. </plug> (The chapter is slightly out of date with respect to the latest and greatest build of Code Contracts, but nothing huge.)
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