身份证号码

偶尔发现身份证号码的规定，觉得甚是好玩，特此标记

 身份证验证算法

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 身份验证算法
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void textBox1_KeyPress(object sender, KeyPressEventArgs e)
        {
            if(e.KeyChar < '0' || e.KeyChar >'9')
            {
                e.Handled = true;
            }

            if((textBox1.SelectionStart == 17) && (e.KeyChar == 'x'||e.KeyChar == 'X'))
            {
                e.Handled = false;
            }
            
            if(e.KeyChar == 8)
            {
                e.Handled = false;
            }

        }

        /// <summary>
        /// 校验身份证信息，如果正确，则返回true，否则false
        /// </summary>
        /// <param name="id"></param>
        /// <returns></returns>
        private bool CheckID(string id)
        {
            //身份证1前17位对应的权值
            int[] w = { 7, 9, 10, 5, 8, 4, 2, 1, 6, 3, 7, 9, 10, 5, 8, 4, 2 };
            string checkW = "10X98765432";
            string num17 = id.Substring(0, 17);
            string num18 = id.Substring(17);

            int sum = 0;
            for (int i = 0 ; i < 17; i++)
            {
                sum += w[i] * Convert.ToInt32(num17[i].ToString());
            }

            int mod = sum % 11;
            string result = checkW[mod].ToString();

            //string类型，忽略大小写的比较
            return num18.Equals(result, StringComparison.OrdinalIgnoreCase);

        }
        private void button1_Click(object sender, EventArgs e)
        {
            int age = 0;
            int year = 0;
            //15位：省（2）市（2）区县（2）年（2）月（2）日（2）+3个序列号[奇数男/偶数女]
            //第7、8位
            string id = textBox1.Text.Trim();//去掉两边的空格
            if(id.Length == 15)
            {
                year = Convert.ToInt32(id.Substring(6,2))+1900;
                //age = DateTime.Now.Year - year;
            }
            //18位：年前面一般都加上19 第18位为校验位，从前面17位计算而来
            else if(id.Length == 18)
            {
                if(!this.CheckID(id))
                {
                    MessageBox.Show("身份证号码有误");
                    return;
                }

                year = Convert.ToInt32(id.Substring(6, 4));
                //age = DateTime.Now.Year - year;
            }
            else
            {
                MessageBox.Show("长度有误");
                return;
            }

            age = DateTime.Now.Year - year;
            if(age >= 18)
            {
                pictureBox1.Visible = true;
            }
            else
            {
                MessageBox.Show("nothing");
            }
        }

        private void Form1_Load(object sender, EventArgs e)
        {

        }

    }
}