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

namespace IDprocess
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.Write("请输入身份证号：");
            string idnumber = Console.ReadLine().Trim();
            ID oneID = new ID(idnumber);
            if (oneID.IsValid())
                Console.WriteLine("您的出生日期是：" + oneID.getBirthday().ToString("yyyy年M月d日"));
            else
                Console.WriteLine("对不起，身份证号码错误！");
            Console.Read();
        }
    }
    class ID
    {
        private string IDnumber;
        public ID(string idnumber)
        {
            this.IDnumber = idnumber.Trim();
        }
        //判断是否为有效的身份证号码：
        public bool IsValid()
        {
            int year, month,day ;
            if (IDnumber.Length == 15)
            {
                for (int i = 0; i < 15; i++)
                {
                    //如果有非数字，则无效，返回false
                    if (!char.IsNumber(IDnumber[i]))
                    {
                        return false;
                    }
                }
                //取得出生年月日：
                year = Int32.Parse("19" + IDnumber.Substring(6, 2));
                month = Int32.Parse(IDnumber.Substring(8, 2));
                day = Int32.Parse(IDnumber.Substring(10, 2));
                //调用方法IsValidBirthday判断是否为有效的出生年月日：
                return IsValidBirthday(year, month, day);
            }
            else if (IDnumber.Length == 18)
            {
                for (int i = 0; i < 17; i++)
                {
                    if (!char.IsNumber(IDnumber[i]))
                    {
                        return false;
                    }
                }
                if (!char.IsNumber(IDnumber[17]) && IDnumber[17] != 'X')
                    return false;
                //取得出生年月日：
                year = Int32.Parse(IDnumber.Substring(6,4));
                month = Int32.Parse(IDnumber.Substring(10, 2));
                day = Int32.Parse(IDnumber.Substring(12, 2));
  //调用方法IsValidBirthday判断是否为有效的出生年月日：
                return IsValidBirthday(year, month, day);
            }
            else
                return false;            
        }
        //判断是否为有效的出生年月日：
        private bool IsValidBirthday(int year,int  month,int day)
        {
            if(year==0) 
                return false;
            if (month<1||month > 12)
                return false;
            //判断天数是否在指定年和月中所限制的天数范围之内。
            if (day < 1 || day > DateTime.DaysInMonth(year, month))
                return false;
            //判断出生日期是否大于现在的日期。
            DateTime Birthday = new DateTime(year, month, day);
            if (Birthday > DateTime.Now)
               return false;
           return true;
        }
       //获取出生日期
        public DateTime getBirthday()
       { 
           DateTime  Birthday;
           int year, month,day ;
           if (IsValid())
           {
               if (IDnumber.Length == 15)
               {
                 year = Int32.Parse("19" + IDnumber.Substring(6, 2));
                 month = Int32.Parse(IDnumber.Substring(8, 2));
                 day = Int32.Parse(IDnumber.Substring(10, 2)); 
                 Birthday = new DateTime(year, month, day);
               }
                
               else 
               {
                  year = Int32.Parse(IDnumber.Substring(6, 4));
                 month = Int32.Parse(IDnumber.Substring(10, 2));
                 day = Int32.Parse(IDnumber.Substring(12, 2));
                        Birthday = new DateTime(year, month, day);
               }
           }
           else Birthday = new DateTime(1, 1, 1);
           return Birthday;
       }
    }
}