实体框架中的复杂关系映射

Question

我正在建立一个预订系统。 我有角色（“ admin”，“ client”，“ employee”，“ student”）的用户。

每个保留必须与角色客户的用户相关联，它可能被分配给角色员工的用户，也可能被分配给角色学生的用户。

因此，在预订类中，我具有用户类型的属性，并用[ForeignKey（“ AnytypeId”）]属性标记了它们，以提示EF关系。

我在http://blog.stevensanderson.com/2011/01/28/mvcscaffolding-one-to-many-relationships/上看到了这样的代码

public class Reservation
{

    public int ReservationID
    {
        get;
        set;
    }

    [Required(ErrorMessage="Please provide a valid date")]
    public DateTime ReservationDate
    {
        get;
        set;
    }
    public DateTime ReservationEnd { get; set; }
    public DateTime EntryDate
    {
        get;
        set;
    }
    public DateTime UpdatedOn
    {
        get;
        set;
    }
    public decimal Ammount
    {
        get;
        set;
    }

    public decimal? Discount { get; set; }

    [DataType(DataType.MultilineText)]
    public string ServiceDetails { get; set; }

    [DataType(DataType.MultilineText)]        
    public string Remarks { get; set; }

    public string VoucherNumber { get; set; }

    public int ServiceID
    {
        get;
        set;
    }
    public Service Service
    {
        get;
        set;
    }

    public string EmployeeId { get; set; }
    [ForeignKey("EmployeeId")]
    public User Employee { get; set; }


    public string ClientId { get; set; }
    [ForeignKey("ClientId")]
    public User Client { get; set; }


    public string StudentId { get; set; }
    [ForeignKey("StudentId")]
    public User Student { get; set; }

}
public class User
{

    //[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    //public Guid UserId { get; set; }

    [Key]
    [Required(ErrorMessage = "User Name is required")]
    [Display(Name = "User Name")]
    [MaxLength(100)]        
    public string UserName { get; set; }

    [Required]
    [MaxLength(64)]
    public byte[] PasswordHash { get; set; }

    [Required]
    [MaxLength(128)]
    public byte[] PasswordSalt { get; set; }

    [Required(ErrorMessage = "Email is required")]
    [DataType(DataType.EmailAddress)]
    [MaxLength(200)]
    public string Email { get; set; }

    [MaxLength(200)]
    public string Comment { get; set; }

    [Display(Name = "Approved?")]
    public bool IsApproved { get; set; }

    [Display(Name = "Crate Date")]
    public DateTime DateCreated { get; set; }

    [Display(Name = "Last Login Date")]
    public DateTime? DateLastLogin { get; set; }

    [Display(Name = "Last Activity Date")]
    public DateTime? DateLastActivity { get; set; }

    [Display(Name = "Last Password Change Date")]
    public DateTime DateLastPasswordChange { get; set; }

    public string address { get; set; }
    public string LastName { get; set; }
    public string FirstName { get; set; }
    public string Phone { get; set; }

    public bool? IsActive { get; set; }

    public int? ClientTypeID { get; set; }
    public virtual ClientType ClientType { get; set; }

    public virtual ICollection<Role> Roles { get; set; }

    public DateTime? PackageValidity { get; set; }


    public virtual ICollection<Reservation> Reservations { get; set; }


}

public class UserMap : EntityTypeConfiguration<User>
{
    public UserMap()
    {
        this.HasMany(u => u.Roles)
         .WithMany(r => r.Users)
         .Map(m =>
         {
             m.ToTable("RoleMemberships");
             m.MapLeftKey("Username");
             m.MapRightKey("RoleName");
         });
    }
}

现在，当我运行我的mvc3 EF代码时，首先使用以下ERD和edmx模型为我动态创建了应用数据库。

现在我遇到的几个问题是：1.当我列出角色客户端的所有用户时，即使他们是数据库中可用的保留，他们的保留属性也始终显示为0。 2.如果我尝试删除在数据库中有保留的角色客户端用户，则会出现以下错误。

DELETE语句与REFERENCE约束“ Reservation_Client”冲突。 在数据库“ CRSDB”的表“ dbo.Reservations”的“ ClientId”列中发生了冲突。 该语句已终止。

我检查了ERD和edmx模型中的区域，是否没有应用级联删除。 在删除角色客户的用户但不删除角色员工或学生的用户时，如何指示EF删除所有保留。

Answer 1

这段代码可以解决问题

public class Reservation
{

    public int ReservationID
    {
        get;
        set;
    }

    [Required(ErrorMessage="Please provide a valid date")]
    public DateTime ReservationDate
    {
        get;
        set;
    }
    public DateTime ReservationEnd { get; set; }
    public DateTime EntryDate
    {
        get;
        set;
    }
    public DateTime UpdatedOn
    {
        get;
        set;
    }
    public decimal Ammount
    {
        get;
        set;
    }

    public decimal? Discount { get; set; }

    [DataType(DataType.MultilineText)]
    public string ServiceDetails { get; set; }

    [DataType(DataType.MultilineText)]        
    public string Remarks { get; set; }

    public String  PaymentMethod { get; set; }
    public string VoucherNumber { get; set; }

    public int ServiceID
    {
        get;
        set;
    }
    public virtual Service Service
    {
        get;
        set;
    }


    public string EmployeeID { get; set; }
    [ForeignKey("EmployeeID")]
    public virtual User Employee { get; set; }


    public string ClientID { get; set; }
    [ForeignKey("ClientID")]
    public virtual User Client { get; set; }


    public string StudentID { get; set; }
    [ForeignKey("StudentID")]
    public virtual User Student { get; set; }


}

public class ReservationMap : EntityTypeConfiguration<Reservation>
{
    public ReservationMap()
    {
        this.HasOptional(r => r.Client).WithMany().WillCascadeOnDelete(true);
        this.HasOptional(r => r.Employee).WithMany().WillCascadeOnDelete(false);
        this.HasOptional(r=>r.Student).WithMany().WillCascadeOnDelete(false);
    }
}