根据身份证号判断是否成年（18周岁）？

Question

有18位或15位

Answer 1

            String str = "256954198806182158";            if (str.Length == 18)
            {
                str = str.Substring(6,8);
                DateTime dt;
                if (DateTime.TryParseExact(str, "yyyyMMdd", null, System.Globalization.DateTimeStyles.None, out dt))
                {
                    if (DateTime.Now.Subtract(dt).Days / 365 > 18)
                        Console.WriteLine("18");
                }
            }

Answer 2

下面是我的方法貌似效率不高
public string GetUserState(string num)
    {//420802198807222351
        string state = "";
        if (num != "")
        {
            string d="";
            TimeSpan ts = new TimeSpan();
            DateTime dt = new DateTime();
            if (num.Length == 18) 
            {
          d=  num.Substring(6,8);
           dt = DateTime.ParseExact(d, "yyyyMMdd",null);
      
                
            }
            else if(num.Length==15)
            {
                d = num.Substring(6, 6);
                 dt = DateTime.ParseExact(d, "yyMMdd", null);
               
            }
            ts = DateTime.Now.Subtract(dt);
            DateTime now = DateTime.Now;
            if ((now.Year - dt.Year) > 18)
            {
                state = "已成年，未纳入防沉迷系统";
            }
            else
            {
                if (now.Month >= dt.Month && now.Day >= dt.Day)
                {
                    state = "已成年，未纳入防沉迷系统";
                }
                else
                {
                    state = "未成年，纳入防沉迷系统";
                }
            }
            //state = ts.ToString();        }
        return state;    }

Answer 3

写个例子吧string str=substring("211320198310312116",7,8);
string da=DataTime.Now.ToString("yyMMdd");
int i=Convert.ToInt32(str);
int j=Convert.ToInt32(da);
int k=j-i;
if (k>18)
messagebox.show("成年");
else
messagebox.show("未成年");

Answer 4

public string GetUserState(string num)
    {//420802198807222351
        string state = "";
        if (num != "")
        {
            string d="";
            TimeSpan ts = new TimeSpan();
            DateTime dt = new DateTime();
            if (num.Length == 18) 
            {
          d=  num.Substring(6,8);
           dt = DateTime.ParseExact(d, "yyyyMMdd",null);
      
                
            }
            else if(num.Length==15)
            {
                d = num.Substring(6, 6);
                 dt = DateTime.ParseExact(d, "yyMMdd", null);
               
            }
            ts = DateTime.Now.Subtract(dt);
            DateTime now = DateTime.Now;
            if ((now.Year - dt.Year) > 18)
            {
                state = "已成年，未纳入防沉迷系统";
            }
            else
            {
                if (now.Month >= dt.Month && now.Day >= dt.Day)
                {
                    state = "已成年，未纳入防沉迷系统";
                }
                else
                {
                    state = "未成年，纳入防沉迷系统";
                }
            }
            //state = ts.ToString();        }
        return state;    }

Answer 5

总体算法如下：获取生日，
用生日和当前时间，
比较看看是否大于18。每一步都不难，分解一下把：
获取生日就是截取字符串，
比较就用时间函数，如果不要求严格，可以用年份相减我正在使用《Csdn收音机》第一时间获取最新动态！

Answer 6

最终代码，刚才后面忘记了判断 public string GetUserState(string num)
    {//420802198807222351
        string state = "";
        if (num != "")
        {
            string d="";
            TimeSpan ts = new TimeSpan();
            DateTime dt = new DateTime();
            if (num.Length == 18) 
            {
          d=  num.Substring(6,8);
                
           dt = DateTime.ParseExact(d, "yyyyMMdd",null);
      
                
            }
            else if(num.Length==15)
            {
                d = num.Substring(6, 6);
                 dt = DateTime.ParseExact(d, "yyMMdd", null);
               
            }
            ts = DateTime.Now.Subtract(dt);
            DateTime now = DateTime.Now;
            if ((now.Year - dt.Year) > 18)
            {
                state = "已成年，未纳入防沉迷系统";
            }
            else
            {
                if (now.Month > dt.Month )
                {
                    state = "已成年，未纳入防沉迷系统";
                }
                else
                {
                    if (now.Day >= dt.Day)
                    {
                        state = "已成年，未纳入防沉迷系统";
                    }
                    else 
                    {
                        state = "未成年，纳入防沉迷系统";
                    }
                }
            }
            //state = ts.ToString();        }
        return state;    }