/// <summary>         /// 判断是否闰年？         /// </summary>         /// <param name="a_year"></param>         /// <returns></returns>         public static bool IsLeapYear(int a_year)         {             String s;             DateTime dt;             try             {                 s = (a_year.ToString() + "-02-29");                 dt = Convert.ToDateTime(s);                 return true;             }             catch             {                 return false;             }         }