根據生日計算年齡

偷個懶唄，收藏一些經常使用的方法，之後備用
        private string GetAge(string birthday)
        {
            string strAge = string.Empty;                         // 年齡的字符串表示
            int intYear = 0;                                    // 歲
            int intMonth = 0;                                    // 月
            int intDay = 0;                                    // 天

            DateTime dtNow = DateTime.Now;
            // 若是沒有設定出生日期, 返回空
            if (string.IsNullOrEmpty(birthday))
            {
                return string.Empty;
            }

            // 計算天數
            intDay = dtNow.Day - DateTime.Parse(birthday).Day;
            if (intDay < 0)
            {
                dtNow = dtNow.AddMonths(-1);
                intDay += DateTime.DaysInMonth(dtNow.Year, dtNow.Month);
            }

            // 計算月數
            intMonth = dtNow.Month - DateTime.Parse(birthday).Month;
            if (intMonth < 0)
            {
                intMonth += 12;
                dtNow = dtNow.AddYears(-1);
            }

            // 計算年數
            intYear = dtNow.Year - DateTime.Parse(birthday).Year;

            // 格式化年齡輸出
            if (intYear >= 1)                                            // 年份輸出
            {
                strAge = intYear.ToString() + "歲";
            }

            if (intMonth > 0 && intYear <= 5)                           // 五歲如下能夠輸出月數
            {
                strAge += intMonth.ToString() + "月";
            }

            if (intDay >= 0 && intYear < 1)                              // 一歲如下能夠輸出天數
            {
                if (strAge.Length == 0 || intDay > 0)
                {
                    strAge += intDay.ToString() + "日";
                }
            }

            return strAge;
        }