class ClassA<T>

{

  private T a;

  private T b;

  public ClassA(T a , T b)

  {

    this.a = a;

    this.b = b;

  }

  public string GetSum()

  {

  dynamic num1 = a;

  dynamic num2 = b;

  }

}

dynamic:动态类型， 动态类型可以进行+运算

而 泛型  不可以使用+运算。

 class ClassA<T>
    {
        private T a;
        private T b;

        public ClassA(T a, T b)
        {
            this.a = a;
            this.b = b;
        }
        public T GetSum()
        {
            dynamic num1 = a;
            dynamic num2 = b;
            return (T)(num1+num2);
        }
    }
static void test02()
        {
            ClassA<int> c1 = new ClassA<int>(45,65);
            int res = c1.GetSum();
            Console.WriteLine(res);
            ClassA<string> c2 = new ClassA<string>("hello ", "world");
            string str1 = c2.GetSum();
            Console.WriteLine(str1);
        }
        
        static void Main(string[] args)
        {
            //test01();
            test02();
        }

dynamic  动态类型