public static string FormatDateDisplay(DateTime _datetime)

        {

            var ts = DateTime.Now - _datetime;

            if (ts.TotalSeconds < )

            {

                return Math.Floor(ts.TotalSeconds).ToString() + "秒前";

            }

            else if (ts.TotalMinutes < )

            {

                return Math.Floor(ts.TotalMinutes).ToString() + "分钟前";

            }

            else if (ts.TotalHours < )

            {

                return Math.Floor(ts.TotalHours).ToString() + "小时前";

            }

            //今天

            if (DateTime.Now.ToString("yyyyMMdd") == _datetime.ToString("yyyyMMdd"))

            {

                return "今天 " + _datetime.ToString("HH:mm");

            }

            //昨天

            if (DateTime.Now.AddDays(-).ToString("yyyyMMdd") == _datetime.ToString("yyyyMMdd"))

            {

                return "昨天 " + _datetime.ToString("HH:mm");

            }

            //如果年份与当前年份相等

            if (DateTime.Now.Year == _datetime.Year)

            {

                return _datetime.ToString("MM月dd日");

            }

            return _datetime.ToString("yyyy/MM/dd");

        }