過濾IEnumerable子屬性

Question

我試圖帶回一個對象列表。該對象具有第二個類的IEnumerable屬性。我試圖根據條件過濾這個子列表。

有類：

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; } 
} 

這裏就是我試圖讓家長和篩選孩子的EF代碼：

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

    return parents; 
} 

當我把這種方法，我得到一個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. 

鑑於異常提到使用Select，我已經tr IED這樣做太：

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; 
} 

這也吹了起來，讓我有例外：

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

而這正是我所有的想法！我不知道我在做什麼錯，但是這並不覺得它應該像以前一樣艱難，所以我猜測我錯過了Entity Framework的一些非常重要的東西。

Answer 1

啊，好的！我不熟悉Code First（我在項目中使用生成的模型），但我確信EF不認識這些實體是相關的。錯誤消息：「...和實體導航屬性受支持」告訴我你應該定義一個導航屬性（這些實體之間的關係）。

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; } 
}