一个 Rectangle（矩形）类的实现， C# 的基本语法：

using System;

namespace _12_23
{
    class Program
    {
        int lengh = 5;
        int width = 9;
        public int Space()
        {
            return lengh * width;
        }
        public void Print()
        {
            Console.WriteLine("长{0}", lengh);
            Console.WriteLine("宽{0}", width);
            Console.WriteLine("面积{0}", Space());
        }
        static void Main(string[] args)
        {
            Program pro = new Program();
            pro.Space();
            pro.Print();
            Console.ReadKey();
        }
    }
}