how can i calculate the age using the input (String) of the month,day and year?

Question

        string Month, Year, Day;
        Console.Write("\nInsert birth month: ");
        Month = Console.ReadLine();

        if (Month.Equals("null"))
        {
            Console.Write("Insert birth day ");
            Console.Write("\nInsert birth year \n");

            
            Console.WriteLine("BIRTH MONTH:");
            Console.WriteLine("BIRTH DAY:");
            Console.WriteLine("BIRTH Year:");
            Console.WriteLine("BIRTHDAY:");


            Console.ReadKey();
        }
        else
        {
            Console.Write("Insert birth day: ");
            Day = Console.ReadLine();
            Console.Write("Insert birth year: ");
            Year = Console.ReadLine();

            
            Console.WriteLine("BIRTH MONTH: {0}", Month);
            Console.WriteLine("BIRTH DAY: {0}", Day);
            Console.WriteLine("BIRTH YEAR: {0}", Year);
            Console.WriteLine("BIRTHDAY:{0}/{1}/{2}", Month, Day, Year);
           Console.WriteLine("Age: {0}", DateTime.Now.Year - Convert.ToInt32(Year));
           Console.ReadKey();

           the only  variable that i can calculate is the year but when it comes to the month 
           and day it does not show correctly.

            The program runs like this:
            Insert birth month: 04
            Insert birth day:14
            Insert birth year:2000
         
            BIRTH MONTH:04
            BIRTH DAY:14
            BIRTH Year:2000
            BIRTHDAY:04/14/2000
            AGE: 22

The program runs like that because it does not considered the day and month to execute.

    The program should run like this:

            Insert birth month: 04
            Insert birth day:14
            Insert birth year:2000
         
            BIRTH MONTH:04
            BIRTH DAY:14
            BIRTH Year:2000
            BIRTHDAY:04/14/2000
            AGE: 21

As you can see the age is 21 because the month and day which is April 14 is being considered. any there who can help me out?

I used integer first but the "null" word is not working that's why i used string instead to work this out.

The program should run like this if i insert null work:

Insert birth month:null Insert birth day Insert birth year

BIRTH MONTH: BIRTH DAY: BIRTH Year: BIRTHDAY: AGE:

here's my concern how can i calculate age considering the Three main variable which is Month,Day and Year. Thanks in advance

Answer 1

• Calculating age accurately needs lot of condition to check, because of leap year considerations Refer more on here : How do I calculate someone's age based on a DateTime type birthday?

  using System;
  
  namespace ConsoleApp2
  {
  internal class Program
  {
        static void Main(string[] args)
          {
  
              string FirstName, LastName = " ";
              char MiddleInitial = ' ';
  
              Console.Write("Insert  first name: ");
              FirstName = Console.ReadLine();
  
              if (FirstName.Equals("null"))
              {
                  Console.Write("Insert middle initial ");
                  Console.Write("\nInsert last name \n");
  
              }
              else
              {
                  Console.Write("Insert middle initial: ");
                  MiddleInitial = Console.ReadLine()[0];
                  Console.Write("Insert  last name: ");
                  LastName = Console.ReadLine();
              }
              string Month = "", Year = "", Day = "";
              Console.Write("\nInsert birth month: ");
              Month = Console.ReadLine();
  
  
              if (Month.Equals("null"))
              {
                  Console.Write("Insert birth day ");
                  Console.Write("\nInsert birth year \n");
  
                  Console.WriteLine("\nYour record");
                  Console.WriteLine("FIRST NAME:{0}", FirstName == "null" ? "" : FirstName);
                  Console.WriteLine("MIDDLE INITIAL: {0}", MiddleInitial);
                  Console.WriteLine("LASTNAME: {0}", LastName);
                  Console.WriteLine("BIRTH MONTH:");
                  Console.WriteLine("BIRTH DAY:");
                  Console.WriteLine("BIRTH Year:");
                  Console.WriteLine("BIRTHDAY:");
  
  
                  Console.ReadKey();
              }
              else
              {
                  Console.Write("Insert birth day: ");
                  Day = Console.ReadLine();
                  Console.Write("Insert birth year: ");
                  Year = Console.ReadLine();
  
                  var DOB = string.Format($"{Day}/{Month }  / {Year}");
  
                  var currentdate = DateTime.Now;
                  var age = Age(DateTime.Parse(DOB), currentdate);
  
                  Console.WriteLine("\nYour record");
                  Console.WriteLine("FIRST NAME:{0}", FirstName == "null" ? "" : FirstName);
                  Console.WriteLine("MIDDLE INITIAL: {0}", MiddleInitial);
                  Console.WriteLine("LASTNAME: {0}", LastName);
                  Console.WriteLine("BIRTH MONTH: {0}", Month);
                  Console.WriteLine("BIRTH DAY: {0}", Day);
                  Console.WriteLine("BIRTH YEAR: {0}", DateTime.Now.Year - Convert.ToInt32(Year));
                  Console.WriteLine("BIRTHDAY:{0}/{1}/{2}", Month, Day, Year);
                  Console.WriteLine("Age: {0} ", age);
              }
          }
  
          public static int Age(DateTime birthDate, DateTime laterDate)
          {
              int age;
              age = laterDate.Year - birthDate.Year;
  
              if (age > 0)
              {
                  age -= Convert.ToInt32(laterDate.Date < birthDate.Date.AddYears(age));
              }
              else
              {
                  age = 0;
              }
  
              return age;
          }
  
  
      }
  
  
  }