C# in Depth

C# 2’s syntactic sugar for nullable types121doesn’t mention it, and the documentation for Nullable itself doesn’t mention it.I’ve honored that difference by waiting until we’re specifically talking about C# 2itself before introducing the term.With that out of the way, let’s see what features C# 2 gives us, starting by reducingthe clutter in our code.4.3.1 The ? modifierThere are some elements of syntax that may be unfamiliar at first but have an appropriatefeel to them. The conditional operator (a ? b : c) is one of them for me—it asksa question and then has two corresponding answers. In the same way, the ? operatorfor nullable types just feels right to me.It’s a shorthand way of using a nullable type, so instead of using Nullable we can use byte? throughout our code. The two are interchangeable and compile toexactly the same IL, so you can mix and match them if you want to, but on behalf ofwhoever reads your code next, I’d urge you to pick one way or the other and use itconsistently. Listing 4.3 is exactly equivalent to listing 4.2 but uses the ? modifier.Listing 4.3The same code as listing 4.2 but using the ? modifierint? nullable = 5;object boxed = nullable;Console.WriteLine(boxed.GetType());int normal = (int)boxed;Console.WriteLine(normal);nullable = (int?)boxed;Console.WriteLine(nullable);nullable = new int?();boxed = nullable;Console.WriteLine (boxed==null);nullable = (int?)boxed;Console.WriteLine(nullable.HasValue);I won’t go through what the code does or how it does it, because the result is exactly thesame as listing 4.2. The two listings compile down to the same IL—they’re just using differentsyntax, just as using int is interchangeable with System.Int32. The only changesare the ones in bold. You can use the shorthand version everywhere, including inmethod signatures, typeof expressions, casts, and the like.The reason I feel the modifier is very well chosen is that it adds an air of uncertaintyto the nature of the variable. Does the variable nullable in listing 4.3 have aninteger value? Well, at any particular time it might, or it might be the null value. Fromnow on, we’ll use the ? modifier in all the examples—it’s neater, and it’s arguably theidiomatic way to use nullable types in C# 2. However, you may feel that it’s too easy tomiss when reading the code, in which case there’s certainly nothing to stop you fromusing the longer syntax. You may wish to compare the listings in this section and theprevious one to see which you find clearer.Licensed to Rhona Hadida