[Evolution in aciton] C#1.1=>2.0=>3.0 [Querying Collections]

If want filter out a price greater than $10 ,in the products. we need to loop around,testing each element and printing it out where appropriate.

 

Looping ,testing,printing out C#1.1 static void Main()         {             ArrayList products = Product.GetSampleProducts();             foreach (Product product in products)             {                 if (product.Price > 10m)                 {                     Console.WriteLine(product);                 }             }         }  The dependency is obvious because of the nesting.

C#2.0 Lets us flatten things out a bit  static void Main()         {             //Get Products and Save to List<T>             List<Product> products = Product.GetSampleProducts();             //Define filter              Predicate<Product> filterPrice = delegate(Product product)             {                 return product.Price > 10m;             };             //FindAll this in List<Product>             List<Product> matchPrice = products.FindAll(filterPrice);              //Define print out            Action<Product> printPrices = delegate(Product product)             {                 Console.WriteLine(product);             };              matchPrice.ForEach(printPrices);         }    In particular, it makes it very easy to change the condition we're testing for and the aciton we take on each of the matchs independently. * The FindAll and ForEach methods in C#2.0 just help to encourage you to consider separation of concerns.

So, we could have put all the testing and printing into one statment.[C#2.0] static void Main()        {            List<Product> products = Product.GetSampleProducts();            products.FindAll(delegate(Product p)                                          { return p.Price > 10; })                          .ForEach(delegate(Product p)                                         { Console.WriteLine(p); }                                       );        } That's a bit better, But it is getting in the way Developer , and adding noise to the code, which hurts readability. I still prefer the C#1.1 version.

C#3.0             improves matters dramatically by removing a lot of the fluff surrounding the actual logic of the delegate.  static void Main()         {             List<Product> products = Product.GetSampleProducts();             foreach (Product product in products.Where(p => p.Price > 10))             {                 Console.WriteLine(product);             }         }

So much For this!