多对多LINQ“IN”查询

Question

编辑：下面的答案都有效。我的问题是由于使用NHibernate的LINQ提供程序 这样的：

from parks in Session.Linq<Park>() 

，而不是像这样：

from parks in Session.Linq<Park().AsEnumerable() 

---

我有一个叫公园类，它有一个设施。我想创建一个LINQ查询，它返回列表中包含每个Amenity的所有Park对象。因此，考虑：

List<Park> Parks(IList<Amenity> amenities) 
{ 
    // I want a query that would look like this (if this worked) 
    // return all Park objects that have all of the given amenities 

    var query = from parks in db.Parks 
       where parks.Amenities.Contains(amenities) 
       select parks; 
} 

这个查询：

var query = from parks in Session.Linq<Park>() 
    where amenities.All(a => parks.Amenities.Contains(a)) 
    select parks; 

不起作用。

这里有更多的我的代码上下文：

类映射（我 “米使用功能NHibernate）

public ParkDBMap() 
{ 
Id(x => x.ParkId).Column("ParkId").GeneratedBy.HiLo("0").UnsavedValue(0); 
Map(x => x.Name, "Name"); 
this.HasManyToMany<Amenity>(x => x.Amenities) 
.Table("ParksMaps_ParkAmenities") 
.Cascade.SaveUpdate(); 
} 


public AmenityDBMap() 
{ 
Id(x => x.AmenityId).Column("AmenityId").GeneratedBy.HiLo("0").UnsavedValue(0); 
Map(x => x.Name, "Name"); 
} 

试验方法：

public void ListParksByAmenity() 
{ 
// Create Parks 
int parkCount = 10; 
CreateParks(parkCount); 

// Create Amenities 
Amenity restrooms = new Amenity(); 
restrooms.Name = "Restrooms"; 
ParksRepos.SaveAmenity(restrooms); 

Amenity tennis = new Amenity(); 
tennis.Name = "Tennis Courts"; 
ParksRepos.SaveAmenity(tennis); 

Amenity dogs = new Amenity(); 
dogs.Name = "Dogs Allowed"; 
ParksRepos.SaveAmenity(dogs); 

// Add amenities to parks 
IList<Park> parks = ParksRepos.Parks(); 

parks[0].AddAmenity(dogs); 
parks[0].AddAmenity(tennis); 
parks[0].AddAmenity(restrooms); 
ParksRepos.SavePark(parks[0]); 

parks[4].AddAmenity(tennis); 
parks[4].AddAmenity(restrooms); 
ParksRepos.SavePark(parks[4]); 

parks[9].AddAmenity(restrooms); 
ParksRepos.SavePark(parks[4]); 

IList<Amenity> amenityList = new List<Amenity>() { restrooms}; 
List<Park> restroomsParks = ParksRepos.Parks(amenityList); 

// three parks have restrooms 
Assert.AreEqual(1, restroomsParks.Count); 
Assert.AreEqual(parks[0].Name, restroomsParks[0].Name); 

amenityList = new List<Amenity>() { dogs, tennis, restrooms }; 
List<Park> allAmenities = ParksRepos.Parks(amenityList); 

// only one park has all three amenities 
Assert.AreEqual(3, allAmenities.Count); 

} 

我有三个表A”公园“桌子，”便利设施“桌子，以及具有两列，一个公园ID和一个设施ID的多对多桌子

我在缠绕这个问题时遇到了麻烦。任何人有任何建议？

Answer 1

List<Park> Parks(IList<Amenity> amenities) 
{ 
    var query = from parks in db.Parks 
       where amenities.All(a => parks.Amenities.Where(sa => sa.ID == a.ID).Count() == 1) 
       select parks; 
} 

Answer 2

这将工作。它将返回一个IEnumerable。要转换到列表，你需要做一个ToList（） 注意我假定Park.Amenity是一个列表

var x = from Park p in db.Parks where amenities.Except(p.Amenity).Count() == 0 select p;