EF Code First Many to Many BaseEntity Inheritance

Question

I would like all my entities that are inheriting BaseEntity to have collection of one entity, this is my Sample

public abstract class BaseEntity : IEntity
{
    [Key]
    public Guid Id { get; set; }

    public virtual ICollection<Note> Notes { get; set; }

    protected BaseEntity()
    {
        Id = Guid.NewGuid();
        Notes = new List<Note>();
    }
}

public class Note
{
    [Key]
    public Guid Id { get; set; }
    public string Name { get; set; }
    public string Value { get; set; }

    public Note()
    {
        Id = Guid.NewGuid();
    }
}

public class Student : BaseEntity
{
    public string Name { get; set; }
    public School School { get; set; }
    public string SomeInfo { get; set; }
}

public class School : BaseEntity
{
    public string Name { get; set; }
    public int Rating { get; set; }
    public int Size { get; set; }
}

I would like to map it something like that, because by default table Notes has all ids of all tables (Student_Id, School_Id, etc)

Any Ideas how to do this, or what to search?

Answer 1

You can add an ObjectId to the notes table, to point to the related object (student, school, etc). And decorate your base class with the [ForeignKey("ObjectId")] attribute.

public abstract class BaseEntity : IEntity
{
    [Key]
    public Guid Id { get; set; }

    [ForeignKey("ObjectId")]
    public virtual ICollection<Note> Notes { get; set; }

    protected BaseEntity()
    {
        Id = Guid.NewGuid();
        Notes = new List<Note>();
    }
}

public class Note
{
    [Key]
    public Guid Id { get; set; }
    public Guid ObjectId { get; set; } //student, school, etc
    public string Name { get; set; }
    public string Value { get; set; }

    public Note()
    {
        Id = Guid.NewGuid();
    }
}

This is one to many relationship, and does not require a mapping table, as you are using Guids as primary keys, you do not need to worry about object ids repeating in different tables.