C#类和构造函数的实例

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;


namespace WindowsFormsApp2
{
    public class Point
    {
        public int x;
        public int y;
        public Point(int a=3,int b=4)
        {
            x = a;
            y = b;
        }
        public void setx(int a)
        {
            x = a;
        }
    }
    public partial class Form1 : Form
    {
        Point aa = new Point();
        
        public Form1()
        {
            InitializeComponent();
            //aa.x = 100;
        }

        private void button1_Click(object sender, EventArgs e)
        {

            aa.x ++;
            label1.Text = aa.x.ToString();
        }
    }
}

类的定义，和构造函数：

 public class Point
    {
        public int x;
        public int y;
        public Point(int a=3,int b=4) //构造函数可以设置初始值，如果引用不设置初始值就是默认值。
        {
            x = a;
            y = b;
        }
        public void setx(int a)
        {
            x = a;
        }
    }

转载于:https://my.oschina.net/9ybx/blog/2938411