EF中的多对多映射

Question

We have a case in EF:

We have 3 entities, say User, Role and Department. A User can play one or more roles in each department and that can be active or inactive. So, the columns in Mapping table are as follows:

UserId, RoleId, DeptId, IsActive

We are currently managing the mapping by creating another entity for mapping table, which forces to perform delete operations manually if I have to delete a relationship.

IS there a way this can be achieved without any entity for mapping table.

Thanks in advance.

Answer 1

No, you cannot avoid junction entity creation, because it does not contain only foreign keys - you have IsActive column. Ie its not pure join table (PJT):

Entity Framework (Entity Framework) creates many-to-many relationships in the data model when the join table that represents a many-to-many relationship contains only keys. When Entity Framework creates a data model, it does not represent the PJT table directly in the data model. Instead, Entity Framework creates a direct-navigation relationship between the related tables, known as a many-to-many association.

But in your case even removing additional column will not help, because Entity Framework need to have collection of joined entities on each side (ie direct-navigation relationship). But thus you are joining each entity with other two, you cannot have this collection without providing additional junction entity.

UPDATE: You can configure cascade deletion for this relationship with WillCascadeOnDelete :

modelBuilder.Entity<User>()
    .HasMany(u => u.RoleDepartments)
    .WithRequired(urd => urd.User)
    .WillCascadeOnDelete();

modelBuilder.Entity<Role>()
    .HasMany(r => r.UserDepartments)
    .WithRequired(urd => urd.Role)
    .WillCascadeOnDelete();

modelBuilder.Entity<Department>()
    .HasMany(d => d.UserRoles)
    .WithRequired(urd => urd.Department)
    .WillCascadeOnDelete();