C# in Depth

Advanced generics85implement IEquatable to give a strongly typed API that willavoid unnecessary execution time checks. The equality and hash-code computationsboth use the default equality comparer for the two type parameters—these handlenulls for us automatically, which makes the code somewhat simpler. 5If we wanted to support sorting, we could implement IComparer , perhaps ordering by the first component and then the second.This kind of type is a good candidate for bearing in mind what functionality you mightwant, but not actually implementing until you need it.We’ve finished looking at our “intermediate” features now. I realize it can all seemcomplicated at first sight, but don’t be put off: the benefits far outweigh the addedcomplexity. Over time they become second nature. Now that you’ve got the Pair classas an example, it might be worth looking over your own code base to see whetherthere are some patterns that you keep reimplementing solely to use different types.With any large topic there is always more to learn. The next section will take youthrough the most important advanced topics in generics. If you’re feeling a bit overwhelmedby now, you might want to skip to the relative comfort of section 3.5, where weexplore the generic collections provided in the framework. It’s well worth understandingthe topics in the next section eventually, but if everything so far has been new to youit wouldn’t hurt to skip it for the moment.3.4 Advanced genericsYou may be expecting me to claim that in the rest of this chapter we’ll be coveringevery aspect of generics that we haven’t looked at so far. However, there are so many littlenooks and crannies involving generics, that’s simply not possible—or at least, I certainlywouldn’t want to even read about all the details, let alone write about them.Fortunately the nice people at Microsoft and ECMA have written all the details in thefreely available language specification, 6 so if you ever want to check some obscure situationthat isn’t covered here, that should be your next port of call. Arguably if yourcode ends up in a corner case complicated enough that you need to consult the specificationto work out what it should do, you should refactor it into a more obvious formanyway; you don’t want each maintenance engineer from now until eternity to have toread the specification.My aim with this section is to cover everything you’re likely to want to know aboutgenerics. It talks more about the CLR and framework side of things than the particularsyntax of the C# 2 language, although of course it’s all relevant when developingin C# 2. We’ll start by considering static members of generic types, including type initialization.From there, it’s a natural step to wonder just how all this is implemented5The formula used for calculating the hash code based on the two “part” results comes from reading EffectiveJava (Prentice Hall PTR, 2001) by Joshua Bloch. It certainly doesn’t guarantee a good distribution of hashcodes, but in my opinion it’s better than using a bitwise exclusive OR. See Effective Java for more details, andindeed for many other useful tips.6http://www.ecma-international.org/publications/standards/Ecma-334.htmLicensed to Rhona Hadida