实体框架6 - 嵌套查询中的空值与选择

Question

我在EF6中遇到问题。当我执行查询Select时，它返回值。但是当我添加Select时，它返回null。

的代码是在这里：

的（W）不为null这里...

 var list = db.X.Include("Y").Include("Z.W") 
      .OrderBy(c => c.Id) 
      .Skip(pageSize * page) 
      .Take(pageSize) 
      .ToList(); 

这里，W值是空...

 var list = db.X.Include("Y").Include("Z.W") 
      .Select(a => new { a.Id, a.Z}) 
      .OrderBy(c => c.Id) 
      .Skip(pageSize * page) 
      .Take(pageSize) 
      .ToList(); 

请帮助:)

UPDATE 1

public class academy 
{ 
    public int Id { get; set; } 
    [StringLength(255)] 
    [Index(IsUnique = true)] 
    public string Name { get; set; } 
    public string Logo { get; set; } 
    [Required] 
    public Owner owner { get; set; } 

    public List<location> Location { get; set; }   
} 


public class location 
{ 
    public int Id { get; set; } 
    public string Latitude { get; set; } 
    public string Longitude { get; set; } 
    public string City { get; set; } 
    public string Region { get; set; } 
    public string Neighborhood { get; set; } 
    public string Street { get; set; } 

    public academy Academy { get; set; } 

    public List<stadium> Stadiums { get; set; } 

    public List<Administrators> Administrators { get; set; } 

    public List<addition> Addition { get; set; } 

    public List<Pricing> Pricing { get; set; } 

    public List<time_frame> TimeFrames { get; set; } 

    [NotMapped] 
    public string Details { 
     get { return (City + " - " + Street); } 
    } 

} 


public class Pricing 
{ 

    public int Id { get; set; } 
    public double Price { get; set; } 
    public double? PriceAfterOffer { get; set; } 
    public DateTime? StartDate { get; set; } 
    public DateTime? EndDate { get; set; } 

    public location Location { get; set; } 
    public players_capacity StadiumCapacity { get; set; } 


} 

public class players_capacity 
{ 
    public int Id { get; set; } 
    [StringLength(255)] 
    [Index(IsUnique = true)] 
    public string Capacity { get; set; } 

} 


     var list = db.locations 
      .Select(a => new { a.Id, a.City, a.Region, a.Street, a.Latitude, a.Longitude, a.Pricing, a.Academy }) 
      .OrderBy(c => c.Id) 
      .Skip(pageSize * page) 
      .Take(pageSize) 
      .ToList(); 

的问题是players_capacity总是空

Answer 1

通过Include指定的任何附加数据如果查询修改“形”，在这种情况下，所以他们是你的额外.Select表达失效以前Include条款被忽略忽略。如果您执行GroupBy或GroupJoin，则会发生同样的情况。

幸运的修复很简单：明确指定您的投影Y和Z.W成员：

var list = db.X 
    .Select(x => new { x.Id, x.Z, x.Y, x.Z.W }) 
    .OrderBy(p => p.Id) 
    .Skip(pageSize * page) 
    .Take(pageSize) 
    .ToList();