C# in Depth

Inline delegate actions with anonymous methods147usual “braces on a line on their own” rule for anonymous methods (as I do for trivialproperties) but still allow a decent amount of whitespace. I’d usually write the last lineof listing 5.6 as something likex.ForEach(delegate(int n){ Console.WriteLine(Math.Sqrt(n)); });The parentheses and braces are now less confusing, and the “what it does” part standsout appropriately. Of course, how you space out your code is entirely your own business,but I encourage you to actively think about where you want to strike the balance,and talk about it with your teammates to try to achieve some consistency. Consistencydoesn’t always lead to the most readable code, however—sometimes keeping everythingon one line is the most straightforward format.You should also consider how much code it makes sense to include in anonymousmethods. The first two examples in listing 5.5 are reasonable , but printMean is probablydoing enough work to make it worth having as a separate method. Again, it’s a balancingact.So far the only interaction we’ve had with the calling code is through parameters.What about return values?5.4.2 Returning values from anonymous methodsThe Action delegate has a void return type, so we haven’t had to return anythingfrom our anonymous methods. To demonstrate how we can do so when we need to,we’ll use the new Predicate delegate type. We saw this briefly in chapter 3, buthere’s its signature just as a reminder:public delegate bool Predicate(T obj)Listing 5.7 shows an anonymous method creating an instance of Predicate toreturn whether the argument passed in is odd or even. Predicates are usually used infiltering and matching—you could use the code in listing 5.7 to filter a list to one containingjust the even elements, for instance.Listing 5.7Returning a value from an anonymous methodPredicate isEven = delegate(int x){ return x%2 == 0; };Console.WriteLine(isEven(1));Console.WriteLine(isEven(4));The new syntax is almost certainly what you’d have expected—we just return theappropriate value as if the anonymous method were a normal method. You may haveexpected to see a return type declared near the parameter type, but there’s no need.The compiler just checks that all the possible return values are compatible with thedeclared return type of the delegate type it’s trying to convert the anonymousmethod into.Licensed to Rhona Hadida