C# in Depth

Evolution in action: examples of code change11benefits of C# 3. When the individual pieces of data querying and manipulation are sosimple, larger transformations can still remain compact and readable in one piece ofcode. That in turn encourages a more “data-centric” way of looking at the world.We’ve seen a bit more of the power of C# 2 and 3 in this section, with quite a lot of(as yet) unexplained syntax, but even without understanding the details we can seethe progress toward clearer, simpler code. Figure 1.2 shows that evolution.C# 1Weakly typed comparatorNo delegate sorting optionC# 2Strongly typed comparatorDelegate comparisonsAnonymous methodsC# 3Lambda expressionsExtension methodsOption of leaving list unsortedFigure 1.2 Features involved in making sorting easier in C# 2 and 3That’s it for sorting. Let’s do a different form of data manipulation now—querying.1.1.3 Querying collectionsOur next task is to find all the elements of the list that match a certain criterion—in particular,those with a price greater than $10. In C# 1, we need to loop around, testing eachelement and printing it out where appropriate (see listing 1.9).Listing 1.9 Looping, testing, printing out (C# 1)ArrayList products = Product.GetSampleProducts();foreach (Product product in products){if (product.Price > 10m){Console.WriteLine(product);}}OK, this is not difficult code to understand. However, it’s worth bearing in mind howintertwined the three tasks are—looping with foreach, testing the criterion with if,then displaying the product with Console.WriteLine. The dependency is obviousbecause of the nesting. C# 2 lets us flatten things out a bit (see listing 1.10).Listing 1.10 Separating testing from printing (C# 2)List products = Product.GetSampleProducts();Predicate test = delegate(Product p){ return p.Price > 10m; };List matches = products.FindAll(test);Action print = delegate(Product p){ Console.WriteLine (p); };matches.ForEach (print);Licensed to Rhona Hadida