c# 获取 本周、本月、本季度、本年 的开始时间或结束时间

方式一，

#region 获取 本周、本月、本季度、本年 的开始时间或结束时间
        /// <summary>
        /// 获取开始时间
        /// </summary>
        /// <param name="TimeType">Week、Month、Season、Year</param>
        /// <param name="now"></param>
        /// <returns></returns>
        public static DateTime? GetTimeStartByType(string TimeType, DateTime now)
        {
            switch (TimeType)
            {
                case "Week":
                    return now.AddDays(-(int)now.DayOfWeek + 1);
                case "Month":
                    return now.AddDays(-now.Day + 1);
                case "Season":
                    var time = now.AddMonths(0 - ((now.Month - 1) % 3));
                    return time.AddDays(-time.Day + 1);
                case "Year":
                    return now.AddDays(-now.DayOfYear + 1);
                default:
                    return null;
            }
        }

        /// <summary>
        /// 获取结束时间
        /// </summary>
        /// <param name="TimeType">Week、Month、Season、Year</param>
        /// <param name="now"></param>
        /// <returns></returns>
        public static DateTime? GetTimeEndByType(string TimeType, DateTime now)
        {
            switch (TimeType)
            {
                case "Week":
                    return now.AddDays(7 - (int)now.DayOfWeek);
                case "Month":
                    return now.AddMonths(1).AddDays(-now.AddMonths(1).Day + 1).AddDays(-1);
                case "Season":
                    var time = now.AddMonths((3 - ((now.Month - 1) % 3) - 1));
                    return time.AddMonths(1).AddDays(-time.AddMonths(1).Day + 1).AddDays(-1);
                case "Year":
                    var time2 = now.AddYears(1);
                    return time2.AddDays(-time2.DayOfYear);
                default :
                    return null;
            }
        }
        #endregion　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　

方式二，

public enum DataTimeType
{
    Week,
    Month,
    Season,
    Year
}

    /// <summary>
    /// 获取开始时间
    /// </summary>
    /// <param name="type"></param>
    /// <param name="time"></param>
    /// <returns></returns>
    public static DateTime GetTimeStartByType(DataTimeType type, DateTime time)
    {
        switch (type)
        {
            case DataTimeType.Week:
                return time.AddDays(-(int)time.DayOfWeek + 1);
            case DataTimeType.Month:
                return time.AddDays(-(int)time.Day + 1);
            case DataTimeType.Season:
                var time1 = time.AddMonths(0 - ((time.Month - 1) % 3));
                return time1.AddDays(-time1.Day + 1);
            case DataTimeType.Year:
                return time.AddDays(-(int)time.DayOfYear + 1);
            default:
                return time.AddDays(-(int)time.DayOfWeek + 1);
                
        }
    }
 

 

    /// <summary>
    /// 获取结束时间
    /// </summary>
    /// <param name="DataTimeType">Week、Month、Season、Year</param>
    /// <param name="now"></param>
    /// <returns></returns>
    public static DateTime GetTimeEndByType(DataTimeType type, DateTime now)
    {
        switch (type)
        {
            case DataTimeType.Week:
                return now.AddDays(7 - (int)now.DayOfWeek);
            case DataTimeType.Month:
                return now.AddMonths(1).AddDays(-now.AddMonths(1).Day + 1).AddDays(-1);
            case DataTimeType.Season:
                var time = now.AddMonths((3 - ((now.Month - 1) % 3) - 1));
                return time.AddMonths(1).AddDays(-time.AddMonths(1).Day + 1).AddDays(-1);
            case DataTimeType.Year:
                var time2 = now.AddYears(1);
                return time2.AddDays(-time2.DayOfYear);
            default:
                return now.AddDays(7 - (int)now.DayOfWeek);
        }
    }