泛型

    public class Dog

    {

        private string name;

        public Dog(string name)
        {

            this.name = name;

        }
        public void PrintName()
        {
            Console.WriteLine(name);
        }
        /// <summary>
        /// 定义泛型方法IsHappy<T>(T target)定义在普通类当中 +
        /// 方法名IsHappy+泛型参数T,可以是多个参数可以是一个参数(可以是任何类型，int啊，类啊都行)+
        /// 参数名T target
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="target"></param>
        public void IsHappy<T>(T target) where T: class//对方法名IsHappy添加约束，只允许类类型，则int型等其他类型会报错
        {
            Console.WriteLine("Happy:" + target.ToString());
        }
    }

    public class Cat

    {
        private string name;    

        public Cat(string name)
        {

            this.name = name;

        }
        public void PrintName()
        {
            Console.WriteLine(name);
        }

    }

    class shit
    {

    }

    class Program
    {
        static void Main(string[] args)
        {
            var dog = new Dog("A");
            dog.IsHappy<shit>(new shit());//狗看到狗屎很开心
            //dog.IsHappy<int>(3);//狗看到数字3很开心，未添加约束时可以生效
            //自从添加了约束（public void IsHappy<T>(T target) where T: class），int类型不再可用
            dog.IsHappy<Cat>(new Cat("Tom"));//狗看到Tom猫很开心，未添加约束时可以生效
        }
    }