C# Linq到实体-重用具有导航属性的谓词?
我试图找到一种在EF 6.1.3中重用谓词来过滤实体的方法。我在使用“Where”筛选相关属性时遇到问题 例如,如果我有此界面C# Linq到实体-重用具有导航属性的谓词?,c#,linq,entity-framework,navigation-properties,C#,Linq,Entity Framework,Navigation Properties,我试图找到一种在EF 6.1.3中重用谓词来过滤实体的方法。我在使用“Where”筛选相关属性时遇到问题 例如,如果我有此界面IValidFromTo public interface IValidFromTo { DateTime StartDate { get; set;} DateTime EndDate { get; set; } } 以及一个返回谓词的函数,其中: public class Extensions { public static Expression&
IValidFromTo
public interface IValidFromTo
{
DateTime StartDate { get; set;}
DateTime EndDate { get; set; }
}
以及一个返回谓词的函数,其中
:
public class Extensions
{
public static Expression<Func<T, bool>> Current<T>()
where T : IValidFromTo
{
var currentDate = DateTime.Now;
return x => x.StartDate <= currentDate && x.EndDate >= currentDate;
}
}
我想把它投射到一个包含人名和当前项的对象中,最后得到一些相当混乱的代码:
var relationQuery = ctx.People.Select(x => new
{ Name = x.Name,
CurrentItems = x.Items.AsQueryable().Where(Extensions.Current<Item>())
});
如果每个人可能有多个有效项目
,则
var grouped = peopleWithValid.GroupBy(x => x.Person);
但是,此版本的查询将排除没有匹配项的人员
var relationQuery = ctx.People.Select(x => new
{ Name = x.Name,
CurrentItems = x.Items.AsQueryable().Where(Extensions.Current<Item>())
});
CurrentItems = x.Items.Current() // quasi an extension method on `ICollection<Item>`?
var isCurrent= x => <<some condition on x>>;
...
var validItems = ctx.Items.Where(isCurrent);
var peopleWithCurrentItems = from person in ctx.Persons
join item in validItems on person.Id equals item.Owner.Id
select new { Person = person, Item = item };
var grouped = peopleWithValid.GroupBy(x => x.Person);