Question

＆安培;＆安培; z.DisplayDurations.Count＆gt; 0这是场景。有2个实体类：

class DisplayDuration
{
    public int DisplayDurationID { get; set; }
    public double Seconds { get; set; }
    public string SecondsString { get; set; }
    public int? FK_Zone { get; set; }
    public double? BasePrice { get; set; }
    public bool? IsActive { get; set; }
}

class Zone
{
    public int ZoneID { get; set; }
    public int FK_ProductID { get; set; }
    public string Name { get; set; }
    public double Width { get; set; }
    public double Height { get; set; }
    public bool Active { get; set; }
    public string Description { get; set; }

    public virtual List<DisplayDuration> DisplayDurations { get; set; } //Contains the list of DisplayDuration
}

现在当我尝试获取基于DisplayCount的区域列表时，所有DisplayDuration关于该zoneid所有DisplayDuration出现，而我只想要DisplayDuration与IsActive值＆＃34; True＆＃34;。有没有办法实现它。我这样做。

    public List<Zone> RetrieveActiveZonesHavingDDurations()
    {
        var zone = from z in _context.Zones
                   where z.Active &&  && z.DisplayDurations.Count > 0
                   select z;
        return zone.ToList();
    }

Answer 1

由于无法过滤关联属性（即仅获取活动的DisplayDurations），并且无法在Linq-to-entities中构造实体，因此您需要匿名对象或模拟Zone的中间类。

public class ZoneModel
{
    public int ZoneID { get; set; }
    public int FK_ProductID { get; set; }
    public string Name { get; set; }
    public double Width { get; set; }
    public double Height { get; set; }
    public bool Active { get; set; }
    public string Description { get; set; }

    public virtual IEnumerable<DisplayDuration> DisplayDurations { get; set; }
}

现在你可以这样做：

var zones = _context.Zones
    .Where(z => z.Active && z.DisplayDuration.Count>0)
    .Select(z => new ZoneModel
    {
        ZoneID = z.ZoneID,
        FK_ProductID = z.FK_ProductID,
        Name = z.Name,
        Width = z.Width,
        Height = z.Height,
        Active = z.Active,
        Description = z.Description,
        DisplayDurations = z.DisplayDurations
            .Where(d => d.IsActive.HasValue && d.IsActive.Value==true)
    });

Answer 2

更新您的方法，如下所示。

public List<Zone> RetrieveActiveZonesHavingDDurations()
{
    var zone = from z in _context.Zones
                   where z.Active
                   && z.DisplayDurations != null
                   && z.DisplayDurations.Count > 0
                   && z.DisplayDurations.Any<DisplayDurations>(x => x.IsActive == true)
               select z;

    return zone.ToList();

}

检索IsActive Column为True的记录。实体框架和LINQ

2 个答案: