EF Core - 包含 ThenInclude 接口

Question

我正在尝试使用 .Include().ThenInclude() 加载相关数据。我正在使用继承，我的 class 派生自基础 class TicketEntry 可以实现一个接口 IApprovable:

public class Ticket
{
    [Key]
    public int Id { get; set; }

    [Required]
    public string Title { get; set; }

    public ICollection<TicketEntry> TicketEntries { get; set; }
}

public abstract class TicketEntry
{
    [Key]
    public int Id { get; set; }

    [Required]
    [DatabaseGenerated(DatabaseGeneratedOption.Computed)]
    public DateTime CreationDate { get; set; }

    [Required]
    public string UserId { get; set; }
    [ForeignKey("UserId")]
    public ApplicationUser User { get; set; }

    public int TicketId { get; set; }
    [ForeignKey("TicketId")]
    public Ticket Ticket { get; set; }
}

public class Common : TicketEntry
{
    [Required]
    public string Description { get; set; }
}

public class CostEstimate : TicketEntry, IApprovable
{
    [Required]
    [Column(TypeName = "money")]
    public decimal Estimate { get; set; }

    public Boolean? Approved { get; set; }

    public string ApprovingUserId { get; set; }
    [ForeignKey("ApprovingUserId")]
    public ApplicationUser ApprovingUser { get; set; }
}

现在我想获得一个 Ticket 及其所有 TicketEntries 及其 User 和实现接口 IApprovable.[=19 的所有 TicketEntries 的 ApprovingUser =]

我试过这样做：

_context.Ticket
    .Include(t => t.TicketEntries)
        .ThenInclude(te => te.User)
    .Include(t => t.TicketEntries as ICollection<IApprovable>)
        .ThenInclude(ia => ia.ApprovingUser)

这不起作用，因为它不是纯属性表达式。

我试图查找类似的案例，但没有找到。我是不是遗漏了什么或者根本不可能，我正在尝试做一些你通常不应该做的事情？

即使不应该，您将如何完成？

Answer 1

无法在 EntityFramework Core 2.0 或更早版本中包含派生。

有一个 GitHub 问题 Query: Support Include/ThenInclude for navigation on derived type 请求此功能，该功能已添加到 EntityFramework Core 2.1-preview1。

根据 2.1 documentation and What's new in 2.1，您可以通过以下语法之一使用它：

var option1 = context.People.Include(p => ((Student)p).School);
var option2 = context.People.Include(p => (p as Student).School);
var option3 = context.People.Include("School");

更新：构建 2018 公告和生产就绪

https://blogs.msdn.microsoft.com/dotnet/2018/05/07/announcing-entity-framework-core-2-1-rc-1/

Today, we are excited to announce that the first release candidate of EF Core 2.1 is available, alongside .NET Core 2.1 RC 1 and ASP.NET Core 2.1 RC 1, for broad testing, and now also for production use!

EF Core - 包含 ThenInclude 接口

EF Core - Include ThenInclude Interface

c#

asp.net-core

entity-framework-core

ef-core-2.0

更新：构建 2018 公告和生产就绪