过滤IEnumerable子属性

Question

我试图带回一个对象列表。该对象具有第二个类的IEnumerable属性。我试图根据条件过滤这个子列表。

有类：

public class Parent 
{ 
    public int Id { get; set; } 
    public string Title { get; set; } 
    public bool Active { get; set; } 
    public virtual IEnumerable<Child> Children { get; set; } 
} 

public class Child 
{ 
    public int Id { get; set; } 
    public string Title { get; set; } 
    public int ParentId { get; set; } 
    public int OtherId { get; set; } 
    public bool Active { get; set; } 
    public virtual Parent Parent { get; set; } 
} 

这里就是我试图让家长和筛选孩子的EF代码：

public IEnumerable<ParentViewModel> GetParents(int otherId) 
{ 
    var parents = _databaseContext.Parents 
     .Include(i => i.Children.Where(child => child.OtherId == otherId)); 

    return parents; 
} 

当我把这种方法，我得到一个ArgumentException，消息：

The Include path expression must refer to a navigation property defined on the type. 
Use dotted paths for reference navigation properties and the Select operator for 
collection navigation properties. 

鉴于异常提到使用Select，我已经tr IED这样做太：

public IEnumerable<ParentViewModel> GetParents(int otherId) 
{ 
    var parents = _databaseContext.Parents 
     .Where(parent => parent.Active == true) 
     .Include(parent => parent.Children); 
     .Select(parent => new 
     { 
      Active = parent.Active, 
      Id = parent.Id, 
      Children = parent.Children 
       .Where(child => child.OtherId == propertyId) 
       .Select(child => new 
       { 
        Active = child.Active, 
        Id = child.Id, 
        ParentId = child.ParentId, 
        OtherId = child.OtherId, 
        Title = child.Title 
       }, 
      Title = parent.Title 
     }); 
    return parents; 
} 

这也吹了起来，让我有例外：

The specified type member 'Children' is not supported in LINQ to 
Entities. Only initializers, entity members, and entity navigation 
properties are supported. 

而这正是我所有的想法！我不知道我在做什么错，但是这并不觉得它应该像以前一样艰难，所以我猜测我错过了Entity Framework的一些非常重要的东西。

Answer 1

啊，好的！我不熟悉Code First（我在项目中使用生成的模型），但我确信EF不认识这些实体是相关的。错误消息：“...和实体导航属性受支持”告诉我你应该定义一个导航属性（这些实体之间的关系）。

public class Parent 
{ 
    [Key] 
    public int Id { get; set; } 
    public string Title { get; set; } 
    public bool Active { get; set; } 
    public virtual ICollection<Child> Children { get; set; } 
} 

public class Child 
{ 
    [Key] 
    public int Id { get; set; } 
    public string Title { get; set; } 
    public int ParentId { get; set; } 
    public int OtherId { get; set; } 
    public bool Active { get; set; } 
    public int ParentId [get;set;} 
    [ForeignKey("ParentId")] 
    public virtual Parent Parent { get; set; } 
}