C＃日期范围过滤器

Question

我需要按日期范围过滤记录，可以是自定义的或预定义的。为此，我实现了以下代码，但我感觉它仍然可以优化。我想听听意见和建议。

public static DateTime StartOfWeek(this DateTime dt, DayOfWeek startOfWeek)
{
    int diff = dt.DayOfWeek - startOfWeek;
    if (diff < 0)
    {
        diff += 7;
    }

    return dt.AddDays(-1 * diff).Date;
}

public enum DateRange
{

    Last24Hours = 1,
    Today = 2,
    Yesterday = 3,
    LastWeek = 4,
    ThisWeek = 5,
    LastMonth = 6,
    Custom = 0

}

public class DateRangeFilter
{
    internal static readonly DateTime DefaultDateTime = DateTime.MinValue;

    private DateRange? _period;
    public DateRange? Period
    {
        get
        {
            if (_reportStartDate != DefaultDateTime && _reportEndDate != DefaultDateTime)
            {
                _period = DateRange.Custom;
            }
            else
            {
                _period = !_period.HasValue ? DateRange.ThisWeek : _period;
            }
            return _period;
        }
        set
        {
            _period = value;
        }
    }

    private DateTime _reportStartDate;
    public DateTime StartDate
    {
        get { return Period == DateRange.Custom ? GetFormatedDate(_reportStartDate) : GetDateRange(true); }
        set { _reportStartDate = value; }
    }

    private DateTime _reportEndDate;
    public DateTime EndDate
    {
        get { return Period == DateRange.Custom ? GetFormatedDate(_reportEndDate, false) : GetDateRange(false); }
        set { _reportEndDate = value; }
    }

    private static DateTime GetFormatedDate(DateTime dt, bool isStartDate = true)
    {
        var h = (isStartDate) ? 0 : 23;
        var m = (isStartDate) ? 0 : 59;
        var s = (isStartDate) ? 0 : 59;
        return new DateTime(dt.Year, dt.Month, dt.Day, h, m, s);
    }

    private DateTime GetDateRange(bool isStartDate)
    {
        var returnDate = DateTime.UtcNow;
        var y = DateTime.UtcNow.AddDays(-1);
        var yesterday = new DateTime(y.Year, y.Month, y.Day, 23, 59, 59);
        var h = (isStartDate) ? 0 : 23;
        var m = (isStartDate) ? 0 : 59;
        var s = (isStartDate) ? 0 : 59;

        switch (Period)
        {

            case DateRange.Today:
                returnDate = (isStartDate) ? new DateTime(returnDate.Year, returnDate.Month, returnDate.Day, h, m, s) : returnDate;
                break;
            case DateRange.Yesterday:
                returnDate = (isStartDate) ? new DateTime(y.Year, y.Month, y.Day, h, m, s) : yesterday;
                break;
            case DateRange.Last24Hours:
                returnDate = (isStartDate) ? returnDate.AddHours(-24) : returnDate;
                break;
            case DateRange.LastWeek:
                var first = returnDate.AddDays(-(int)returnDate.DayOfWeek - 6);
                var last = first.AddDays(6);
                first = new DateTime(first.Year, first.Month, first.Day, h, m, s);
                returnDate = (isStartDate) ? first : new DateTime(last.Year, last.Month, last.Day, h, m, s);
                break;
            case DateRange.ThisWeek:
                var startOfWeek = returnDate.StartOfWeek(DayOfWeek.Monday);
                var lastDayOfWeek = startOfWeek.AddDays(6);
                lastDayOfWeek = new DateTime(lastDayOfWeek.Year, lastDayOfWeek.Month, lastDayOfWeek.Day, h, m, s);
                returnDate = (isStartDate) ? startOfWeek : lastDayOfWeek;
                break;
            case DateRange.LastMonth:
                var month = new DateTime(returnDate.Year, returnDate.Month, 1, 0, 0, 0);
                var lastOfMonth = month.AddDays(-1);
                lastOfMonth = new DateTime(lastOfMonth.Year, lastOfMonth.Month, lastOfMonth.Day, h, m, s);
                returnDate = (isStartDate) ? month.AddMonths(-1) : lastOfMonth;
                break;
            case DateRange.Last30Days:
                returnDate = (isStartDate) ? yesterday.AddDays(-30).AddSeconds(1) : yesterday;
                break;
            case DateRange.Last90Days:
                returnDate = (isStartDate) ? yesterday.AddDays(-90).AddSeconds(1) : yesterday;
                break;
        }

        return returnDate;

    }

}

使用：

public GetRecords([FromUri]DateRangeFilter filter) { ... }