using System;
public enum DataTimeType
{
    Week,
    Month,
    Season,
    Year
}
public class DataTimeManager
{
    /// <summary>
    /// 獲取開始時間
    /// </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);
                //return null;
        }
    }

    /// <summary>
    /// 獲取結束時間
    /// </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);
        }
    }
}