c# - Entity Framework 代码优先和链接的实体

Question

我有 AspNetUser 实体:

public partial class AspNetUser
{
    public string Id { get; set; }

    [Required]
    [StringLength(256)]
    [Index(IsClustered = false, IsUnique = true)]
    public string UserName { get; set; }
    ....

接口(interface):

public interface IProfile
{
    string FirstName { get; set; }
    string LastName { get; set; }
    string Nickname { get; set; }
}

public interface IMembershipEntity
{
    string AspNetUserId { get; set; }
    AspNetUser AspNetUser { get; set; }
}

还有 2 个实体，每个实体都作为 FK 链接到 AspNetUser(都实现了 IProfile 和 IMembershipEntity):

public partial class Driver : IMembershipEntity, IProfile
{

    #region IProfile
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string Nickname { get; set; }
    #endregion

    #region IMembershipEntity
    public string AspNetUserId { get; set; }
    [ForeignKey("AspNetUserId")]
    public virtual AspNetUser AspNetUser { get; set; }
    #endregion

   ... driver fields


public class User : BaseEntity, IMembershipEntity, IProfile
{
    #region IMembershipEntity
    public string AspNetUserId { get; set; }
    public virtual AspNetUser AspNetUser { get; set; }
    #endregion

    #region IProfile
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string Nickname { get; set; }
    #endregion

    .... user fields
}

现在我需要一个需要从 AspNetUser 获取 FirstName/LastName 的方法，如下所示:

        var element = (from i in db.AspNetUsers
                    select new UserElementDomain()
                    {
                        UserId = i.Id,
                        CompanyName = i.Company.Name,
                        FirstName = (get FirstName here),
                        LastName = (get LastName here),
                        RoleName = i.AspNetRoles.FirstOrDefault().Name,
                        SMSnumber = i.SMSnumber,
                        UserName = i.UserName,
                        .....
                    }).FirstOrDefault();

怎么做？我可以向 AspNetUser 添加 2 个属性，例如:

    public virtual User User { get; set; }
    public virtual Driver Driver { get; set; }

但是怎么说，它应该是一个或零个链接，而不创建 UserId/DriverId

即使有了它，我也必须编写如下代码:

FirstName = (i.User!=null)? i.User.FirstName : ((i.Driver!=null)?i.Driver.FirstName : String.Empty)

而且我不喜欢这段代码，因为当我再添加一个实体时，我必须检查所有代码并再添加一个条件。如何正确地做到这一点？可能是使用接口(interface)/继承？

Answer 1

我以前见过重复的代码，但很少见过重复的数据结构。

根据您当前的代码，如果 User.FirstName="A"& Driver.FirstName="B"，则结果仅为“A”。如果您有一个名为“Employee”的新实体，如果您不使用当前样式对其进行硬编码，谁知道哪个名字将是 3 个实体中的真正名字？

您当前的代码可以简化为:

i.User?.FirstName ?? i.Driver?.FirstName ?? i.Whatever?.FirstName ?? String.Empty

但它是您要管理的真实数据吗？

我给你另外两个选择:

1. 将属性添加到根实体，在您的例子中是 AspNetUser:

   public class AspNetUser
   {
   ....
   public string FirstName { get; set; }
   public string LastName { get; set; }
   public string Nickname { get; set; }
   ....
   }
   

2. 管理 1 个实体中的通用配置文件

   public class AspNetUser
   {
   ....
   public virtual AspNetUserProfile AspNetUserProfile { get; set; }
   }
   public class AspNetUserProfile
   {
   [Key]
   public string Id { get; set; }
   
   public string FirstName { get; set; }
   public string LastName { get; set; }
   public string Nickname { get; set; }
   ....
   [ForeignKey("Id")]
   public virtual AspNetUser AspNetUser { get; set; }
   }
   

然后在你的代码中:

   db.AspNetUsers.Select(i => new UserElementDomain()
                {
                    UserId = i.Id,
                    CompanyName = i.Company.Name,
                    FirstName = i.AspNetUserProfile?.FirstName,
                    LastName = i.AspNetUserProfile?.LastName,
                    RoleName = i.AspNetRoles.FirstOrDefault().Name,
                    SMSnumber = i.SMSnumber,
                    UserName = i.UserName,
                    .....
                })

如果 Driver/User/Empolyee 想要获取 FirstName，只需使用:

Empolyee.AspNetUser.AspNetUserProfile?.FirstName