c# - 带有 3 个外键的 EF 链接表

Question

用户可以访问许多协会。对于给定的用户，我需要为他有权访问的每个关联分配一个工作角色。我如何首先映射 EF 代码中的表？

[User] 
UserId

[Association]
AssocId

[Role]
RoleId

[LNK_User_Assoc_Role]
UserId   [PK]
AssocId  [PK]
RoleId   [FK]

更新: 我认为 octavioccl 是正确的，但我如何将 Assoc 分配给用户？这是我的代码。它不愿意工作:

_user = new USER();
_user.Username = user.Username

DbContext.USERS.Add(_user);
DbContext.SaveChanges();

var newUser = DbContext.USERS.Find(_user.User_Id);                                               

foreach (int assocId in select2)
{
LNK_UserRoleAssoc u = new LNK_UserRoleAssoc();                           
u.User = newUser;
u.Association = DbContext.Associations.Find(assocId);
u.Role = DbContext.ROLES.Find(2);
newUser.UserRoleAssocs.Add(u);                          
}

DbContext.SaveChanges();

Answer 1

有两种方法可以实现您的需求。

1. 使用 Data Annotations :

   public class User{
   
     [Key]
     public Guid UserId {get;set;}
   
     public virtual ICollection<UserRoleAssociation> UserRoleAssociations {get;set;}      
   }
   
   public class Role{
     [Key]
     public Guid RoleId {get;set;}
   
     public virtual ICollection<UserRoleAssociation> UserRoleAssociations {get;set;}
   }
   
   public class Association{
     [Key]
     public Guid AssociationId {get;set;}
   
     public virtual ICollection<UserRoleAssociation> UserRoleAssociations {get;set;}
   }
   
   public class UserRoleAssociation{
   
    [Key,ForeignKey("User"),Column(Order=1)]
    public Guid UserId {get;set;}
   
    [Key,ForeignKey("Role"),Column(Order=2)]
    public Guid RoleId {get;set;}
   
    [Key,ForeignKey("Associoation"),Column(Order=3)]
    public Guid AssociationId {get;set;}
   
    //Navigation Properties
   
    public virtual User User {get;set;}
    public virtual Role Role {get;set;}
    public virtual Association Association {get;set;}
   

2. 使用 Fluent Api .在这种情况下，您不需要在我上面显示的模型中使用任何属性(删除它们)，只需在您的上下文中覆盖 OnModelCreating 方法并添加这些配置:

   protected override void OnModelCreating(DbModelBuilder modelBuilder)
   {
    base.OnModelCreating(modelBuilder);
   
    modelBuilder.Entity<UserRoleAssociation>()
       .HasKey(c => new {c.UserId, c.RoleId, c.AssociationId});
   
    modelBuilder.Entity<UserRoleAssociation>()
       .HasRequired(p => p.User)
       .WithMany(u => u.UserRoleAssociations)
       .HasForeignKey(p => p.UserId);
   
    modelBuilder.Entity<UserRoleAssociation>()
       .HasRequired(p => p.Role)
       .WithMany(r => r.UserRoleAssociations)
       .HasForeignKey(p => p.RoleId);
   
    modelBuilder.Entity<UserRoleAssociation>()
       .HasRequired(p => p.Association)
       .WithMany(a => a.UserRoleAssociations)
       .HasForeignKey(p => p.AssociationId);
   }