Calculate Age based on Visit Date

Question

I need to write C# code to calculate a person's age based on a birthdate and a fixed exam visit date.

Currently the code is written like this:

public static int CalculateAge(string birthdate)
{
  DateTime dob = DateTime.Parse(birthdate);

  int age = DateTime.Now.Year - dob.Year;
  if (DateTime.Now.Month < dob.Month)                         
  {
    age--;
  }
  else if (DateTime.Now.Month == dob.Month &&
    DateTime.Now.Day < dob.Day)
  {
    age--;
  }

  return age;
}

I need to pass in a second variable called ExamDate to figure out the age. The way it is currently written, when the FastReport is run say 3 years down the road, obviously someone who is 22 now would be 25 when the report is displayed. I know we can't use DateTime.Now

Answer 1

Pass the second date as parameter, and change all occurrences from DateTime.Now to this date:

public static int CalculateAge(string birthdate, string examDate)
{
  DateTime dob = DateTime.Parse(birthdate);
  DateTime ed = DateTime.Parse(examDate);

  int age = ed.Year - dob.Year;
  if (ed.Month < dob.Month)                         
  {
    age--;
  }
  else if (ed.Month == dob.Month &&
    ed.Day < dob.Day)
  {
    age--;
  }

  return age;
}

So when you will pass person date of birth and date of the exam, the result will be always the same.