c#根据生日和当前日期计算年龄源代码， 方法名： GetAge(DateTime birthDay, DateTime endDate, ref int age)
返回一个 整形的年龄和一个带单位的年龄

      /// <summary>
        /// 点击按钮测试年龄方法
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void button1_Click(object sender, EventArgs e)
        {
            int age = 0;
            DateTime dt1 = new DateTime();
            DateTime dt2 = new DateTime();
            dt1 = DateTime.Parse("2001-01-01");
            dt2 = DateTime.Parse("2020-01-01");
            GetAge(dt1, dt2, ref age);
            MessageBox.Show(GetAge(dt1, dt2, ref age));
            MessageBox.Show(age.ToString());
        }
测试结果如下：

        /// <summary>
        /// 根据出生日期获取年龄（不随时间变化）
        /// </summary>
        /// <param name="birthDay">生日</param>
        /// <param name="endDate">指定的日期</param>
        /// <param name="age">年龄整形</param>
        /// <returns></returns>
        public string GetAge(DateTime birthDay, DateTime endDate, ref int age)
        {
            string result = "";
            if (endDate.Date.CompareTo(birthDay.Date) >= 0)
            {
                TimeSpan time = endDate - birthDay;
                int diffYear = endDate.Year - birthDay.Year;
                int diffMonth = endDate.Month - birthDay.Month;
                int diffDay = endDate.Day - birthDay.Day;
                int diffHour = endDate.Hour - birthDay.Hour;
                int diffMinute = endDate.Minute - birthDay.Minute;
                int diffSecond = endDate.Second - birthDay.Second;

                //小于一天的
                if (time.Days < 1)
                {
                    if (time.Hours != 0)
                    {
                        result = time.Hours.ToString() + "时";
                    }
                    else
                    {
                        result = "1时";
                    }

                    age = 0;
                    return result;
                }
                else
                {
                    #region 算法先将所有为负数的值变为正数
                    if (diffSecond < 0)
                    {
                        diffMinute = diffMinute - 1;
                        diffSecond = diffSecond + 60;
                    }

                    if (diffMinute < 0)
                    {
                        diffHour = diffHour - 1;
                        diffMinute = 60 + diffMinute;
                    }
                    if (diffHour < 0)
                    {
                        diffDay = diffDay - 1;
                        diffHour = 24 + diffHour;
                    }
                    if (diffDay < 0)
                    {
                        diffDay = (System.DateTime.DaysInMonth(birthDay.Year, birthDay.Month) + endDate.Day) - birthDay.Day;
                        diffMonth = diffMonth - 1;
                    }
                    if (diffMonth < 0)
                    {
                        diffYear = diffYear - 1;
                        diffMonth = diffMonth + 12;
                    }
                    #endregion

                    //age去年龄整数
                    age = diffYear;
                    //大于等于1天小于1月的，精确到小时；
                    if (diffMonth < 1 && diffYear == 0)
                    {
                        if (diffDay != 0 && diffHour != 0)
                        {
                            result = diffDay.ToString() + "天" + diffHour.ToString() + "时";
                        }
                        else if (diffDay == 0)
                        {
                            result = diffHour.ToString() + "时";
                        }
                        else if (diffHour == 0)
                        {
                            result = diffDay.ToString() + "天";
                        }
                        return result;
                    }//大于等于1月且小于1周岁的，精确到天；
                    else if (diffMonth >= 1 && diffYear == 0)
                    {
                        if (diffMonth != 0 && diffDay != 0)
                        {
                            result = diffMonth.ToString() + "月" + diffDay.ToString() + "天";
                        }
                        else if (diffDay == 0)
                        {
                            result = diffMonth.ToString() + "月";
                        }
                        return result;
                    }

                    if (diffYear >= 1 && diffYear < 3)
                    {
                        if (diffMonth != 0 && diffYear != 0)
                        {
                            result = diffYear.ToString() + "岁" + diffMonth.ToString() + "月";
                        }
                        else if (diffMonth == 0)
                        {
                            result = diffYear.ToString() + "岁";
                        }
                        return result;
                    }

                    if (diffYear >= 3)
                    {
                        result = diffYear.ToString() + "岁";
                        return result;
                    }

                }


            }
            return result;
        }

原文链接：http://www.jxszl.com/jlmb/Others/23996.html