如何比较Linq中的年作为日期字段？

Question

我正在使用下面的代码来比较两个日期的年份：

public string GetResultWbyYears()
    {
        using (var context = new DbEntity())
        {
            int yeat = DateTime.Now.Year;
            var holidays = (from rl in context.HolidayMasters
                            where rl.Isactive == true && rl.Isdelete == false //&& rl.HolidayDate.Year == yeat
                            orderby rl.HolidayDate ascending
                            select new HolidayEntity
                            {
                                HolidayDesc = rl.HolidayDesc,
                                HolidayDate = rl.HolidayDate,
                                HolidayId = rl.HolidayId

                            }).ToList().AsEnumerable().Select(x => new HolidayEntity()
            {
                HolidayDesc = x.HolidayDesc,
                HolidayDate = x.HolidayDate,
                Isactive = x.Isactive,
                Isdelete = x.Isdelete,
                HolidayId = x.HolidayId,
                Zones = GetZonesWithSelectedForHolidays(x.HolidayId)
            }).ToList();

            holidays = holidays.Where(n => n.HolidayDate.Year == yeat).ToList();
        }

无法理解上述原因为何不起作用..请帮助我如何按年获取结果。

我在Google上进行了搜索，发现有些文章所做的与我上面所做的相同，但这对我不起作用。 这就是为什么我发布了这个问题。

Answer 1

选择IEnumerable<HolidayEntity> ，然后将其转换为List ，丢失Isactive和Isdelete值，因为它们将是默认值，然后再次选择IEnumerable<HolidayEntity> 。
实际上，这没有必要。

您的LINQ看起来更漂亮：

public string GetResultWbyYears()
{
    int year = DateTime.Now.Year;
    using (var context = new DbEntity())
    {
        var result = context.HolidayMasters
            .Where(hm => hm.Isactive && !hm.Isdelete && hm.HolidayDate.Year == year)
            .OrderBy(hm => hm.HolidayDate)
            .ToList();

        foreach (var item in result)
            item.Zones = GetZonesWithSelectedForHolidays(item.HolidayId); 
    }
}

或者以其他方式：

public string GetResultWbyYears()
{
    int year = DateTime.Now.Year;
    using (var context = new DbEntity())
    {
        var result = (from hm in dbSet
            where hm.Isactive && !hm.Isdelete && hm.HolidayDate.Year == 2015
            orderby hm.HolidayDate ascending
            select hm).ToList();

        foreach (var item in result)
            item.Zones = GetZonesWithSelectedForHolidays(item.HolidayId); 
    }
}    

我想您的context.HolidayMasters类型为DbSet<HolidayEntity ，因为它具有所有具有相同名称的属性。 否则，请使用一个Select ：

public string GetResultWbyYears()
{
    int year = DateTime.Now.Year;
    using (var context = new DbEntity())
    {
        var result = (from hm in dbSet
            where hm.Isactive && !hm.Isdelete && hm.HolidayDate.Year == 2015
            orderby hm.HolidayDate ascending
            select new HolidayEntity {
                HolidayDesc = x.HolidayDesc,
                HolidayDate = x.HolidayDate,
                Isactive = x.Isactive,
                Isdelete = x.Isdelete,
                HolidayId = x.HolidayId,
                Zones = GetZonesWithSelectedForHolidays(x.HolidayId)
            }).ToList();
    }
}