如何在Linq中比较日期字段的年份

本文关键字：字段 日期 比较 Linq | 更新日期: 2023-09-27 18:28:23

我使用以下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();
        }

不明白为什么以上不起作用。。请帮我怎样才能按年份得出结果。

我在谷歌上搜索过，发现一些文章和我上面做的一样，但这对我不起作用。这就是我发布这个问题的原因。

如何在Linq中比较日期字段的年份

选择IEnumerable<HolidayEntity>，然后将其转换为List，丢失默认值Isactive和Isdelete，然后再次选择IEnumerable<HolidayEntity>
实际上没有必要这样做。

你的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); 
    }
}

或者以另一种方式：

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); 
    }
}

我假设您的context.HolidayMasters属于DbSet<HolidayEntity类型，因为它具有相同名称的所有属性。否则，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();
    }
}
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