C# in Depth

192 CHAPTER 7 Concluding C# 2: the final featuresthe class, it prevents any use of it that would require one. For instance, all of the followingare invalid when StringHelper is a static class:StringHelper variable = null;StringHelper[] array = null;public void Method1(StringHelper x) {}public StringHelper Method1() { return null; }List x = new List();None of these are prevented if the class just follows the C# 1 pattern—but all of themare essentially useless. In short, static classes in C# 2 don’t allow you to do anything youcouldn’t do before—but they prevent you from doing things that you shouldn’t havebeen doing anyway.The next feature on our list is one with a more positive feel. It’s aimed at a very specific—althoughwidely encountered—situation, and allows a solution that is neitherugly nor breaks encapsulation, which was the choice available in C# 1.7.3 Separate getter/setter property accessI’ll admit to being slightly bemused when I first saw that C# 1 didn’t allow you to havea public getter and a private setter for properties. This isn’t the only combination ofaccess modifiers that is prohibited by C# 1, but it’s the most commonly desired one. Infact, in C# 1 both the getter and the setter have to have the same accessibility—it’sdeclared as part of the property declaration rather than as part of the getter or setter.There are perfectly good reasons to want different accessibility for the getter andthe setter—often you may want some validation, logging, locking, or other code to beexecuted when changing a variable that backs the property but you don’t want tomake the property writable to code outside the class. In C# 1 the alternatives wereeither to break encapsulation by making the property writable against your betterjudgment or to write a SetXXX() method in the class to do the setting, which franklylooks ugly when you’re used to “real” properties.C# 2 fixes the problem by allowing either the getter or the setter to explicitly have amore restrictive access than that declared for the property itself. This is most easilyseen with an example:string name;public string Name{get { return name; }private set{// Validation, logging etc herename = value;}}In this case, the Name property is effectively read-only to all other types, 2 but we canuse the familiar property syntax for setting the property within the type itself. The2Except nested types, which always have access to private members of their enclosing types.Licensed to Rhona Hadida