基本类型--委托（一）

 15．1初识委托

 //声明一个委托，它的实例引用一个方法，该方法接受一个Int32的参数并返回void
    internal delegate void Feedback(Int32 value);
    public sealed class Program {
        public static void Main() {
            StaticDelegateDemo();
            InstanceDelegateDemo();
            ChainDelegateDemo1(new Program());
            ChainDelegateDemo2(new Program());
        }
        //委托调用静态回调方法
        private static void StaticDelegateDemo() {
            Console.WriteLine("---StaticDelegateDemo---");
            Counter(1, 3, null);
            Counter(1, 3, new Feedback(FeedBackToConsole));
            Counter(1, 3, new Feedback(FeedBackToMsgBox));
            Console.ReadLine();
        }
        //委托调用实例回调方法
        private static void InstanceDelegateDemo() {
            Console.WriteLine("---InstanceDelegateDemo---");
            Program p = new Program();
            Counter(1, 3, new Feedback(p.FeedBackToFile));
            Console.ReadLine();
        }
        //顺序调用多个静态、实例方法
        private static void ChainDelegateDemo1(Program p) {
            Console.WriteLine("---ChainDelegateDemo1---");
            Feedback fb1 = new Feedback(FeedBackToConsole);
            Feedback fb2 = new Feedback(FeedBackToMsgBox);
            Feedback fb3 = new Feedback(p.FeedBackToFile);

            Feedback fbChain = null;
            fbChain = (Feedback)Delegate.Combine(fbChain, fb1);
            fbChain = (Feedback)Delegate.Combine(fbChain, fb2);
            fbChain = (Feedback)Delegate.Combine(fbChain, fb3);
            Counter(4, 5, fbChain);

            Console.WriteLine();
            fbChain = (Feedback)Delegate.Remove(fbChain, new Feedback(FeedBackToMsgBox));
            Counter(6, 7, fbChain);
            Console.ReadLine();
        }
        //顺序调用多个静态、实例方法
        private static void ChainDelegateDemo2(Program p) {
            Console.WriteLine("---ChainDelegateDemo2---");
            Feedback fb1 = new Feedback(FeedBackToConsole);
            Feedback fb2 = new Feedback(FeedBackToMsgBox);
            Feedback fb3 = new Feedback(p.FeedBackToFile);

            Feedback fbChain = null;
            fbChain += fb1;
            fbChain += fb2;
            fbChain += fb3;
            Counter(8, 9, fbChain);

            Console.WriteLine();
            fbChain -= new Feedback(FeedBackToMsgBox);
            Counter(10, 11, fbChain);
            Console.ReadLine();
        }
        //
        private static void Counter(Int32 from, Int32 to, Feedback fb) {
            for (int i = from; i <= to; i++){
                if (fb != null)
                    fb(i);
            }
        }
        private static void FeedBackToConsole(Int32 value) {
            Console.WriteLine("控制台输出：" + value);
        }
        private static void FeedBackToMsgBox(Int32 value) {
            Console.WriteLine("消息框显示：" + value);
        }
        private void FeedBackToFile(Int32 value) {
            StreamWriter sw = new StreamWriter("C:/FeedBackToFile.txt", true);
            sw.WriteLine("文件显示：" + value);
            sw.Close();
        }
    }

15．2使用委托来回调静态方法

15．3使用委托回调实例方法

15．4委托揭秘

15．5使用委托回调多个方法（链式）