01/04

.Net Framework 3.5 Features

• Func<T,TResult>: an encapsulation method with T input and Tresult output
• eg. Func<string, string> selector = str => str.ToUpper();
        string[] words = { "orange", "apple", "Article", "elephant" };
          IEnumerable<String> aWords = words.Select(selector);
• Action<T> : no output
• Anonymous Type : var
• Extension Method
• Property :
• public int NumberOfCars { get; set; }
• Partial Methods ; Object Initialize Syntax
• Point finalPoint = new Point { X = 30, Y = 30 };

 

Linq Sample Code with Func<T>

….

  string[] currentVideoGames = {"Morrowind", "BioShock",
"Half Life 2: Episode 1", "The Darkness",
"Daxter", "System Shock 2"};

            //1.Linq Expression can var
            IEnumerable<string> subset = from game in currentVideoGames
                                         where game.Length > 6
                                         orderby game
                                         select game;
            //2.Lambda Expression can use var
            Func<string, string> newVariable = game => game;
            IEnumerable<string> subset2 = currentVideoGames.Where(game => game.Length > 6).OrderBy(game => game).Select(newVariable);
            //3. Enumerable
            var subset3 = Enumerable.Where(currentVideoGames, game => game.Length > 6).OrderBy(game => game).Select(game => game);

            //4. With Func        

            //Func<string, bool> searchfilter = delegate(string game)
            //                                    {
            //                                        return game.Length > 6;
            //                                    };

            Func<string, bool> searchfilter2 = game => game.Length > 6;
            var subset4 = currentVideoGames.Where(searchfilter2).OrderBy(game => game).Select(game => game);

            // Using oftype<T>
            // Extract the ints from the ArrayList.
            ArrayList myStuff = new ArrayList();
            myStuff.AddRange(new object[] { 10, 400, 8, false, new Object(), "string data" });
            IEnumerable<int> myInts = myStuff.OfType<int>();
            // Prints out 10, 400, and 8.
            foreach (int i in myInts)
            {
                Console.WriteLine("Int value: {0}", i);
            }

            // 封装一个具有一个参数并返回 TResult 参数指定的类型值的方法。
            Func<string, string> convertMeth = delegate(string s)
            {
                return s.ToUpper();
            };
            // Linq Differnce
            List<string> myCars = new List<String> { "Yugo", "Aztec", "BMW" };
            List<string> yourCars = new List<String> { "BMW", "Saab", "Aztec" };
            var carDiff = (from c in myCars select c)
            .Except(from c2 in yourCars select c2);
            Console.WriteLine("Here is what you don't have, but I do:");
            foreach (string s in carDiff)
                Console.WriteLine(s); // Prints Yugo.

….