Question

我有“建筑物”实体，而在该实体内部我还有另一个“公寓”实体。我要过滤那些至少有一个公寓处于“已批准”状态且可访问性为“可出售”的建筑物。

这是我的Building类。

public class Building 
{
 public ICollection<Apartment> Apartments {get;set;}
}

这是我的公寓房。

public class Apartment 
{
  public Enum State {get;set;}   
}

到目前为止，我已经尝试了这段代码，但是看来这实际上是行不通的。

 var buildings = _context.Buildings.Where(apartments.Apartments
              .Any(isActive =>isActive.State == ApartmentState.Approved && isActive.Accessibility == AccessibilityState.Saleable));

此代码仅返回具有至少一个满足此条件的公寓的所有公寓列表。我不需要其余的公寓。

我还尝试了另一种方法来获得理想的结果

var buildings = _context.BuildingsWhere(apartments => apartments.Apartments.Where(apart=> aapart.State == ApartmentState.Approved && apart.Accessibility == AccessibilityState.Saleable));

在这种情况下，我遇到了这个错误

运算符不能应用于bool和IEnumerable类型的操作数

任何帮助将不胜感激。

Answer 1

您正在寻找Any子句：

var buildings = _context
    .Buildings // For all my buildings
    .Where(b => b.Apartments // I want the ones where
        .Any(a => a.State == ApartmentState.Approved // There is at least 1 approved
            && a.Accessibility == AccessibilityState.Saleable)); // AND one is Saleable.

在执行Where时，语句内的最终值必须是布尔值，并且将返回IEnumerable（IQueriable）。 Any将返回true或false供您过滤。

更新：新要求，仅获得具有过滤功能的公寓。

拥有建筑物后，如果您只想要批准且可出售的公寓，则可以再次过滤。

foreach(var building in buildings){
    var saleableApartments = building.Apartments
        .Where(a => a.State == ApartmentState.Approved
                    && a.Accessibility == AccessibilityState.Saleable));
    // Do whatever.
}

或者，如果您只是寻找公寓

var saleableApartments = _context
    .Buildings // For all my buildings
    .Select(b => b.Apartments // Select the apartments
        .Where(a => a.State == ApartmentState.Approved // where x
            && a.Accessibility == AccessibilityState.Saleable));

Answer 2

您的方案需要在linq查询中加入。您可以这样写：

var apartments = from building in _context.Buildings
                join apartment in _context.Apartments on building.Id equals apartment.BuildingID
                where apartment.State == ApartmentState.Approved 
                && apartment.Accessibility == AccessibilityState.Saleable
                select apartment ;

或者您也可以编写一个子查询：

var buildings = _context.Buildings
                  .Select(building => new 
                          { 
                             Building = building ,
                             Apartments = _context.Apartments
                                       .Where(apartment=>
                                        building.Id == apartment.BuildingId &&
                                        apartment.State == ApartmentState.Approved &&
                                        apartment.Accessibility == AccessibilityState.Saleable)
                           });

Answer 3

从@BlueEyedBehemoth答案下的评论中，我建议：

var filteredBuildings = _context
    .Buildings
    .Select(b => new { apparments = b.Appartments
        .Where(a => a.State == ApartmentState.Approved
                          && a.Accessibility == AccessibilityState.Saleable) } )
    .Where(b => b.apparments.Any());

Linq嵌套Where（）子句

3 个答案: