C# 根据出生年月 计算天数/计算X岁X月X天字符串

     public class TimeTool
     {
         //根据出生年月计算 整数天
         private static int GetAgeByBirthdate(DateTime birthdate)
         {
             DateTime now = DateTime.Now;
             int age = now.Year - birthdate.Year;
             if (now.Month < birthdate.Month || (now.Month == birthdate.Month && now.Day < birthdate.Day))
             {
                 age--;
             }
             return age <  ?  : age;
         }
           //根据出生年月计算 X岁或X月X天或X天
         public static string GetAgeByBirthday(DateTime birthday)
         {
             var currenttime = DateTime.Now;
             var diffTime = currenttime - birthday;
             if (diffTime.TotalDays >= )
             {
                 //年龄计算
                 return GetAgeByBirthdate(birthday).ToString() + "岁";
             }
             else
             {
                 //个月计算
                 var diffmonth = currenttime.Month - birthday.Month;
                 var day = currenttime.Day - birthday.Day;
                 if (day < )
                 {
                     diffmonth--;
                 }
                 if (diffmonth > )
                 {
                     DateTime newbirthday = birthday.AddMonths(diffmonth);
                     day = (int)((currenttime - newbirthday).TotalDays);
                     return diffmonth.ToString() + "个月" + (day ==  ? "" : day.ToString() + "天");
                 }
                 else
                 {
                     //直接计算天
                     return ((int)(diffTime.TotalDays)).ToString() + "天";
                 }
             }

         }
     }