实体框架中有多少关系正在发挥作用

Question

I am using C# and Entity framework for building an authorization application. I have user, Role, permission, claim table. As user and Role has many to many relationship, I have created the use-Role table. I have problem with mapping relationship.

This is my User class:

 public class User
     {

    public int UserId { get; set; }

    public string UserName { get; set; }
}

This is my Role class:

public class Role
{
    public int RoleId { get; set; }

    public string RoleName { get; set; }
}

I am not sure what I should have in User-Role class to make the many-to- many relationship work correctly specially when I am doing update.
This is my User-Role class:

 public class UserRole
    {

    public UserRole()
    {
        Roles = new Collection<Role>();
        Users = new Collection<User>();
    }

    public int Id { get; set; }

    public int UserId { get; set; }

    public string UserName { get; set; }

    public int RoleId { get; set; }

    public string RoleName { get; set; }

}

and how the mapping should look like?

Answer 1

First beofre giving you the solution, just know that you are reinventing the wheel. I said that because ASP.Net Identity just make what you are attempting to do.

Anyway some clarifications:

• UserRole is a association entity between User and Role
• UserRole has required Role
• UserRole has required User

UserRole mean a combinaison between one User and one Role . You can have many instances of this as mutch as a User has many Role . This is why before translating it with Fluent API you must remove Roles and Users collections that you put into UserRole and create instead UserRoles as an collection ICollection<UserRole> into User and Role.

Your classes must follow this:

User class:

public class User
{
    public int Id { get; set; }

    public string Name { get; set; }

    public ICollection<UserRole> UserRoles { get; set; }

    public User()
    {
        this.UserRoles = new Collection<UserRole>();
    }
}

Role class:

public class Role
{
    public int Id { get; set; }

    public string Name { get; set; }

    public ICollection<UserRole> UserRoles { get; set; }

    public Role()
    {
        this.UserRoles = new Collection<UserRole>();
    }
}

UserRole class:

public class UserRole
{
    public int Id { get; set; }

    public int UserId { get; set; }

    public User User { get; set; }

    public int RoleId { get; set; }

    public Role Role { get; set; }
}

No configuration needed, EF will use default convention and create all tables needed for you.

In common when your join entity UserRole has no data property, I mean just foreign key, then you can remove it and just let User and Role as follow:

User class:

public class User
{
    public int Id { get; set; }

    public string Name { get; set; }

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

    public User()
    {
        this.Roles = new Collection<Role>();
    }
}

Role class:

public class Role
{
    public int Id { get; set; }

    public string Name { get; set; }

    public ICollection<User> Users { get; set; }

    public Role()
    {
        this.Users = new Collection<User>();
    }
}

Again no configuration needed, EF will create the tables and join table for you by using default conventions.

To learn a lot of things about EF, I recommend this web site Entity Framework Tutorials and if you can just read the following two books :

• Programming Entity Framework: DbContext

• Programming Entity Framework: Code First

Answer 2

If you just add the collection navigation properties to the User and Role entities, EF is going to create a many to many relationship by convention. In this case EF handles the junction table ( UserRoles ) for you, so, you don't need to map it if you don't need it. In summary, your model could be this way:

public class User
{
    public int Id { get; set; }

    public string Name { get; set; }

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

public class Role
{
    public int Id { get; set; }

    public string Name { get; set; }

   public virtual ICollection<User> Users { get; set; }
}

If you need ,for example, change the junction table's name or they PK's names, you can override OnModelCreating method in your context class and add this Fluent Api configuration:

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{

    modelBuilder.Entity<User>()
                .HasMany(s => s.Roles)
                .WithMany(c => c.Users)
                .Map(cs =>
                        {
                            cs.MapLeftKey("UserRefId");
                            cs.MapRightKey("RoleRefId");
                            cs.ToTable("UserRoles");
                        });

} 

And if you are using a mapping class, add the following configuration in the constructor of your UserMap class:

public UserMap()
{

    HasMany(s => s.Roles)
   .WithMany(c => c.Users)
   .Map(cs =>
              {
                 cs.MapLeftKey("UserRefId");
                 cs.MapRightKey("RoleRefId");
                 cs.ToTable("UserRoles");
              });
}

Answer 3

Agree with @octaviocci if you do not require a custom join table between Users and Roles.

However you seem to have a few custom properties in your UserRoles table, like "String Role" so maybe you want to have that join table have some custom fields in it. If that is the case, then try this in your mapping for UserRoles

this.HasRequired(t => t.Roles).WithMany().HasForeignKey(fk => fk.RoleId); this.HasRequired(t => t.Users).WithMany().HasForeignKey(fk => fk.UserId);