How to calculate an age based on a birthday [duplicate]

Question

Possible Duplicate:
How do I calculate someone's age based on a DateTime type birthday?

I want to write an ASP.NET helper method which returns the age of a person given his or her birthday.

I've tried code like this:

public static string Age(this HtmlHelper helper, DateTime birthday) {     return (DateTime.Now - birthday); //?? } 

But it's not working. What is the correct way to calculate the person's age based on their birthday?

Answer 1

Stack Overflow uses such a function to determine the age of a user.

How do I calculate someone's age based on a DateTime type birthday?

The given answer is

DateTime now = DateTime.Today; int age = now.Year - bday.Year; if (now < bday.AddYears(age))      age--; 

So your helper method would look like:

public static string Age(this HtmlHelper helper, DateTime birthday) {     DateTime now = DateTime.Today;     int age = now.Year - birthday.Year;     if (now < birthday.AddYears(age))          age--;      return age.ToString(); } 

Today, I use a different version of this function to include a date of reference. This allow me to get the age of someone at a future date or in the past. This is used for our reservation system, where the age in the future is needed.

public static int GetAge(DateTime reference, DateTime birthday) {     int age = reference.Year - birthday.Year;     if (reference < birthday.AddYears(age))         age--;      return age; } 

Answer 2

Another clever way from that ancient thread:

int age = (     Int32.Parse(DateTime.Today.ToString("yyyyMMdd")) -      Int32.Parse(birthday.ToString("yyyyMMdd"))) / 10000;