C# 操作符重载

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

namespace ConsoleApplication1
{
    class Program
    {

        class CAdd
        {
            public int val;
            public string str;
            public bool bok;

            public static CAdd operator + (CAdd a, CAdd b)
  18:              {
  19:                  CAdd c = new CAdd();
  20:                  c.val = a.val + b.val;
  21:                  c.str = a.str + b.str;
  22:                  c.bok = a.bok && b.bok;
  23:                  return c;
  24:              }

        }

        static void Main(string[] args)
        {
            CAdd a = new CAdd();
            CAdd b = new CAdd();
            CAdd d = new CAdd();

            a.val = 3;
            a.str = "1";
            a.bok = true;

            b.val = 5;
            b.str = "2";
            b.bok = false;

            d.val = 5;
            d.str = "2";
            d.bok = false;

            CAdd c = a + b + d;
            Console.ReadLine();
        }
    }
}