C# in Depth

Novel uses of nullable types131particularly taxing with the if/else version, but I know I’d have to stop and thinktwice, and verify the code mentally. I’d also be relying on unit tests, so there’d be relativelylittle chance of me actually getting it wrong, but I’d prefer not to think aboutthings like this unless I absolutely have to.NOTEEverything in moderation—Just in case you may be thinking that my code islittered with uses of the null coalescing operator, it’s really not. I tend toconsider it when I see defaulting mechanisms involving nulls and possiblythe conditional operator, but it doesn’t come up very often. When its useis natural, however, it can be a powerful tool in the battle for readability.We’ve seen how nullable types can be used for “ordinary” properties of objects—caseswhere we just naturally might not have a value for some particular aspect that is stillbest expressed with a value type. Those are the more obvious uses for nullable typesand indeed the most common ones. However, a few patterns aren’t as obvious but canstill be powerful when you’re used to them. We’ll explore two of these patterns in ournext section. This is more for the sake of interest than as part of learning about thebehavior of nullable types themselves—you now have all the tools you need to usethem in your own code. If you’re interested in quirky ideas and perhaps trying somethingnew, however, read on…4.4 Novel uses of nullable typesBefore nullable types became a reality, I saw lots of people effectively asking for them,usually related to database access. That’s not the only use they can be put to, however.The patterns presented in this section are slightly unconventional but can make codesimpler. If you only ever stick to “normal” idioms of C#, that’s absolutely fine—this sectionmight not be for you, and I have a lot of sympathy with that point of view. I usuallyprefer simple code over code that is “clever”—but if a whole pattern provides benefitswhen it’s known, that sometimes makes the pattern worth learning. Whether or notyou use these techniques is of course entirely up to you—but you may find that theysuggest other ideas to use elsewhere in your code. Without further ado, let’s start withan alternative to the TryXXX pattern mentioned in section 3.2.6.4.4.1 Trying an operation without using output parametersThe pattern of using a return value to say whether or not an operation worked, andan output parameter to return the real result, is becoming an increasingly commonone in the .NET Framework. I have no issues with the aims—the idea that somemethods are likely to fail to perform their primary purpose in nonexceptional circumstancesis common sense. My one problem with it is that I’m just not a huge fanof output parameters. There’s something slightly clumsy about the syntax of declaringa variable on one line, then immediately using it as an output parameter.Methods returning reference types have often used a pattern of returning nullon failure and non-null on success. It doesn’t work so well when null is a valid returnvalue in the success case. Hashtable is an example of both of these statements, in aLicensed to Rhona Hadida