大家好！
我想问的是下题中？处，我用有参构造初始化了，
为什么方法结果和无参一样0 0 0，而不是8 16 15 呢。
          //这是Main下的程序
            //对象1
            Rectangle1 rec = new Rectangle1();
            Console.WriteLine(rec.and());                程序执行后输出0
            Console.WriteLine(rec.perimeter());          程序执行后输出0
            Console.WriteLine(rec.area());               程序执行后输出0
            Console.WriteLine(rec.and(3, 5));            程序执行后输出8
            Console.WriteLine(rec.perimeter(3, 5));      程序执行后输出16
            Console.WriteLine(rec.area(3, 5));           程序执行后输出15
            //对象2
            Rectangle1 rec1 = new Rectangle1(3, 5);      
            Console.WriteLine(rec.and());                程序执行后输出0    ？
            Console.WriteLine(rec.perimeter());          程序执行后输出0    ？
            Console.WriteLine(rec.area());               程序执行后输出0    ？
            Console.WriteLine(rec.and(4, 6));            程序执行后输出10
            Console.WriteLine(rec.perimeter(4, 6));      程序执行后输出20
            Console.WriteLine(rec.area(4, 6));           程序执行后输出24

//这是类中的程序
class Rectangle1
    {
        //两个成员变量
        private int len;
        private int wid;
        //求和
        public int and()
        {
            int an = len + wid;
            return an;
        }
        public int and(int len,int wid)
        {
            int an = len + wid;
            return an;
        }
        //求周长
        public double perimeter()
        {
            double per = 2 * len + 2 * wid;
            return per;
        }
        public double perimeter(int len,int wid)
        {
            double per = 2 * len + 2 * wid;
            return per;
        }
        //求面积
        public double area()
        {
            double are = len * wid;
            return are;
        }
        public double area(int len, int wid)
        {
            double are = len * wid;
            return are;
        }
        //构造函数无参合有参的
        public Rectangle1()
        {
            len = 0;
            wid = 0;
        }
        public Rectangle1(int len,int wid)
        {
            this.len = len;
            this.wid = wid;
        }
    }
            

Rectangle1 rec1 = new Rectangle1(3, 5);      
Console.WriteLine(rec.and());
两个变量名不一致 一个是rec1 一个是rec,
你从头到尾都是用变量rec

修改你说的后问题解决了谢谢呵呵！