c# - Comment puis-je calculer l'âge de quelqu'un déterminé#39;s en fonction d'un anniversaire de type DateTime

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// Save today's date. var today = DateTime.Today;  // Calculate the age. var age = today.Year - birthdate.Year;  // Go back to the year in which the person was born in case of a leap year if (birthdate.Date > today.AddYears(-age)) age--; 

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20080814 - 19800703 = 280111  

int now = int.Parse(DateTime.Now.ToString("yyyyMMdd")); int dob = int.Parse(dateOfBirth.ToString("yyyyMMdd")); int age = (now - dob) / 10000; 

public static Int32 GetAge(this DateTime dateOfBirth) {     var today = DateTime.Today;      var a = (today.Year * 100 + today.Month) * 100 + today.Day;     var b = (dateOfBirth.Year * 100 + dateOfBirth.Month) * 100 + dateOfBirth.Day;      return (a - b) / 10000; } 

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DateTime bDay = new DateTime(2000, 2, 29); DateTime now = new DateTime(2009, 2, 28); MessageBox.Show(string.Format("Test {0} {1} {2}",                 CalculateAgeWrong1(bDay, now),      // outputs 9                 CalculateAgeWrong2(bDay, now),      // outputs 9                 CalculateAgeCorrect(bDay, now),     // outputs 8                 CalculateAgeCorrect2(bDay, now)));  // outputs 8 

public int CalculateAgeWrong1(DateTime birthDate, DateTime now) {     return new DateTime(now.Subtract(birthDate).Ticks).Year - 1; }  public int CalculateAgeWrong2(DateTime birthDate, DateTime now) {     int age = now.Year - birthDate.Year;      if (now < birthDate.AddYears(age))         age--;      return age; }  public int CalculateAgeCorrect(DateTime birthDate, DateTime now) {     int age = now.Year - birthDate.Year;      if (now.Month < birthDate.Month || (now.Month == birthDate.Month && now.Day < birthDate.Day))         age--;      return age; }  public int CalculateAgeCorrect2(DateTime birthDate, DateTime now) {     int age = now.Year - birthDate.Year;      // For leap years we need this     if (birthDate > now.AddYears(-age))          age--;     // Don't use:     // if (birthDate.AddYears(age) > now)      //     age--;      return age; } 

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public static class DateTimeExtensions {     /// <summary>     /// Calculates the age in years of the current System.DateTime object today.     /// </summary>     /// <param name="birthDate">The date of birth</param>     /// <returns>Age in years today. 0 is returned for a future date of birth.</returns>     public static int Age(this DateTime birthDate)     {         return Age(birthDate, DateTime.Today);     }      /// <summary>     /// Calculates the age in years of the current System.DateTime object on a later date.     /// </summary>     /// <param name="birthDate">The date of birth</param>     /// <param name="laterDate">The date on which to calculate the age.</param>     /// <returns>Age in years on a later day. 0 is returned as minimum.</returns>     public static int Age(this 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;     } } 

class Program {     static void Main(string[] args)     {         RunTest();     }      private static void RunTest()     {         DateTime birthDate = new DateTime(2000, 2, 28);         DateTime laterDate = new DateTime(2011, 2, 27);         string iso = "yyyy-MM-dd";          for (int i = 0; i < 3; i++)         {             for (int j = 0; j < 3; j++)             {                 Console.WriteLine("Birth date: " + birthDate.AddDays(i).ToString(iso) + "  Later date: " + laterDate.AddDays(j).ToString(iso) + "  Age: " + birthDate.AddDays(i).Age(laterDate.AddDays(j)).ToString());             }         }          Console.ReadKey();     } } 

{     Birth date: 2000-02-28  Later date: 2011-02-27  Age: 10     Birth date: 2000-02-28  Later date: 2011-02-28  Age: 11     Birth date: 2000-02-28  Later date: 2011-03-01  Age: 11     Birth date: 2000-02-29  Later date: 2011-02-27  Age: 10     Birth date: 2000-02-29  Later date: 2011-02-28  Age: 11     Birth date: 2000-02-29  Later date: 2011-03-01  Age: 11     Birth date: 2000-03-01  Later date: 2011-02-27  Age: 10     Birth date: 2000-03-01  Later date: 2011-02-28  Age: 10     Birth date: 2000-03-01  Later date: 2011-03-01  Age: 11 } 

{     Birth date: 2000-02-28  Later date: 2012-02-28  Age: 12     Birth date: 2000-02-28  Later date: 2012-02-29  Age: 12     Birth date: 2000-02-28  Later date: 2012-03-01  Age: 12     Birth date: 2000-02-29  Later date: 2012-02-28  Age: 11     Birth date: 2000-02-29  Later date: 2012-02-29  Age: 12     Birth date: 2000-02-29  Later date: 2012-03-01  Age: 12     Birth date: 2000-03-01  Later date: 2012-02-28  Age: 11     Birth date: 2000-03-01  Later date: 2012-02-29  Age: 11     Birth date: 2000-03-01  Later date: 2012-03-01  Age: 12 } 

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int age = (int) ((DateTime.Now - bday).TotalDays/365.242199);