C# 初学

突然对C#充满了兴趣，于是兴致勃勃的折腾起来。

下面是折腾的过程：

IDE，我选择了vs2017，不过这货的安装选项略多，对于新手来说各种坑。无论如何，选择”.NET桌面开发”即可，其他的全部留空。

然后新建项目，C#项目，控制台项目。

可以开搞了！

总的来说，C#和Java很像 -- 抽象、虚函数、继承、接口等，然而又具有C++的很多特性，如运算符重载！

using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApp1
{
    class Go
    {
        static void Main(string[] args)
        {
            Cat cat1 = new Cat("a_cat");
            Cat cat2 = new Cat("b_cat");
            Cat cat3 = new Cat("c_cat");

            Console.WriteLine(Animal.Count);
            Console.WriteLine(cat1);

            //测试委托
            DoIt doIt = cat1.Speak;
            doIt += cat2.Speak; //注意，只要方法签名一致即可连续添加
            doIt += cat3.Speak;
            doIt += () =>
            {
                Console.WriteLine("来自Lambda");
            };//lambda
            doIt();

            //测试静态类方法扩展
            Dog dog = new Dog("a_dog");
            dog.Jump();//这个方法，类似于js的apply或者call

            //测试隐式转换
            Cat cat = dog;
            Console.WriteLine(cat);
            //测试显式转换
            dog = (Dog)cat;
            Console.WriteLine(dog);

            //模拟事件
            Client c1 = new Client();
            Client c2 = new Client();

            Animal.NewAnimal += c1.WantAnimal;
            Animal.NewAnimal += c2.WantAnimal;

            Animal dogq = new Dog("Q-dog");

            //测试集合
            ArrayList al = new ArrayList();
            al.Add(cat1);
            al.Add(cat2);
            al.Add(cat3);
            al.Add(cat2);
            Console.WriteLine("ArrayList‘s count is "+al.Count);
            al.Remove(cat2); //只会删除第一个
            Console.WriteLine("ArrayList‘s count is " + al.Count);

            List<Animal> list = new List<Animal>();
            list.Add(cat1);
            list.Add(cat2);
            list.Add(cat3);
            list.Add(cat2);
            Console.WriteLine("List‘s count is " + list.Count);

            Stack<Animal> stack = new Stack<Animal>();
            stack.Push(cat1);
            stack.Push(cat2);
            stack.Push(cat3);
            Console.WriteLine("stack.Peek() = " + stack.Peek() + "; stack.Count = " + stack.Count);
            Console.WriteLine("stack.Pop() = " + stack.Pop() + "; stack.Count = " + stack.Count);

            Queue<Animal> queue = new Queue<Animal>();
            queue.Enqueue(cat1);
            queue.Enqueue(cat2);
            queue.Enqueue(cat3);
            Console.WriteLine("queue.First() = " + queue.First() + "; queue.Count = " + queue.Count);
            Console.WriteLine("queue.Last() = " + queue.Last() + "; queue.Count = " + queue.Count);
            Console.WriteLine("queue.Dequeue() = " + queue.Dequeue() + "; queue.Count = " + queue.Count);

            Dictionary<int, Animal> dic = new Dictionary<int, Animal>();
            dic.Add(1, cat1);
            dic.Add(2, cat2);
            dic.Add(3, cat3);
            Console.WriteLine("dic.Keys = " + dic.Keys + "; dic.Count = " + dic.Count);
            Console.WriteLine("自定义扩展dic.Print() = " + dic.PrintKeys() + "; dic.Count = " + dic.Count);
            Console.WriteLine("自定义扩展dic.PrintValues() = " + dic.PrintValues() + "; dic.Count = " + dic.Count);
            Console.WriteLine(dic);

            Console.ReadLine();
        }
    }

    public delegate void DoIt();//委托，托管一堆方法？！位置，放这里也行？

    interface ISpeak
    {
        void Speak();
    }
    interface IEat
    {
        void Eat();
    }
    class Animal
    {
        protected string _name;
        public static int Count;//用来计数，数一下有多少animal的实例
        public delegate void Handler();//事件订阅
        public static event Handler NewAnimal; //事件

        public Animal() {
            ++Count;
            //通知各位，有新动物来啦
            NewAnimal?.Invoke();
        }
        public Animal(string Name):this()
        {
            _name = Name;
        }
        static Animal()
        {
            Count=0;
        }
        public void setName(string Name)
        {
            _name = Name;
        }
        public string getName()
        {
            return _name ;
        }
        override public string ToString() //重写父类的
        {
            return "Animal[_name="+_name+", Count="+Count+"]";
        }
    }
    //狗类，继承自动物，实现接口
    class Dog : Animal, ISpeak, IEat
    {
        public Dog(string Name) : base(Name) { }
        public void Eat()
        {
            Console.WriteLine("我是一只狗，名字：["+base._name+"]，我在吃狗粮！");
        }

        public void Speak()
        {
            Console.WriteLine("我是一只狗，名字：[" + base._name + "]，汪汪汪！");
        }
        //定义一个隐式转换
        public static implicit operator Cat(Dog dog)
        {
            return new Cat(dog._name);//new 会改变Animal.Count
        }
    }
    //猫类，继承自动物，实现接口
    class Cat : Animal, ISpeak, IEat
    {
        public Cat(string Name) : base(Name) { }
        public void Eat()
        {
            Console.WriteLine("我是一只猫，名字：[" + base._name + "]，我在吃小鱼干~");
        }

        public void Speak()
        {
            Console.WriteLine("我是一只猫，名字：[" + base._name + "]，喵~");
        }

        //定义一个显式转换
        public static explicit operator Dog(Cat cat)
        {
            return new Dog(cat._name);//new 会改变Animal.Count
        }
    }
    //静态类 扩展方法
    static class DogJump
    {
        public static void Jump(this Dog dog)
        {
            Console.WriteLine(dog + " is jumping...");
        }
        public static string PrintKeys(this Dictionary<int, Animal> dic)
        {
            var s="";
            foreach (var item in dic.Keys)
            {
                s += item;
                s += ", ";
            }
            return s;
        }
        public static string PrintValues(this Dictionary<int, Animal> dic)
        {
            var s = "";
            foreach (var item in dic.Values)
            {
                s += item;
                s += ", ";
            }
            return s;
        }
    }

    //定义一个客户类
    class Client
    {
        public void WantAnimal()
        {
            Console.WriteLine("Great! I wanna see it!");
        }
    }

}