Ef core and multiple parent entities use list of the same child entity? - entity-framework

Question

Is there an easy way to have a setup like this in EF Core?
ProjectEntity
Id
Name
List<Notes>
CustomerEntity
Id
Name
List<Notes>
NotesEntity
Id
Date
Note
Every parent entity would have a one-to-many relation to same child entity. So I can not use normal behavior as
NotesEntity
Id
ParentId
Date
Note
I have some idea to have like above but also add one field that said what the parent entity is, is that the right way to do it or is there a better way? If I use this way I can't use EF Core normal behavior with one-to-many relationship? I need to make more manual work for search / add and so on?
Edit :
Entity Framework multiple parent tables I found this solution, but there I need to make a connection from my child to every parent I use, it could be alot of them.
Did also find a solution like :
BaseEntity
List<Notes>
ProjectEntity:BaseEntity
NotesEntity
Id
BaseEntityId
...
This last solution maybe is the best way to do it if I have alot of parent entities?
[EDIT 220922]
Could [Owned] type has collection of other Items? Or this feature won't work on owned entitys? I guess this behavior isn't supported?
[Owned]
public class Note
{
public int Id { get; set; }
public string Text { get; set; }
public int UserId { get; set; }
public User User { get; set; }
public ICollection<string> Tags { get; set; }
}
I got an error on ICollection-row when I try to add-migration.
Unabel to determine the relationshop represented by navigation ... of
typ 'ICollection' Either manually configure the relationship, or
ignore this property using the '[NotMapped]' attribute.....
Maybe I could have one middleentity like :
public class NoteTagsEntity
{
public int Id { get; set; }
public ICollection<string> Tags { get; set; }
}
And then :
[Owned]
public class Note
{
public int Id { get; set; }
public string Text { get; set; }
public int UserId { get; set; }
public User User { get; set; }
public int NoteTagsId { get; set; }
public NoteTagsId NoteTagsId { get; set; }
}
Edit
I solved the Note functionality with having more FK's, one that point to Id of parent and one FK Id that point to what module that use that particular note. Here I don't have parent - child relation in my entities, I need to do this connection by myself but in this way it's easy to apply more modules that use note's later.

Answer 1

Use Owned Entity Types, and each entity will get its own notes table.
eg
public abstract class Entity
{
public int Id { get; set; }
}
public abstract class EntityWithNotes: Entity
{
public virtual ICollection<Note> Notes { get; set; }
}
[Owned]
public class Note
{
public int Id { get; set; }
public string Text { get; set; }
}
public class Project : EntityWithNotes
{
public string Name { get; set; }
}
public class Customer : EntityWithNotes
{
public string Name { get; set; }
}
creates
CREATE TABLE [Customer_Notes] (
[Id] int NOT NULL IDENTITY,
[CustomerId] int NOT NULL,
[Text] nvarchar(max) NOT NULL,
CONSTRAINT [PK_Customer_Notes] PRIMARY KEY ([CustomerId], [Id]),
CONSTRAINT [FK_Customer_Notes_Customer_CustomerId] FOREIGN KEY ([CustomerId]) REFERENCES [Customer] ([Id]) ON DELETE CASCADE
);
CREATE TABLE [Project_Notes] (
[Id] int NOT NULL IDENTITY,
[ProjectId] int NOT NULL,
[Text] nvarchar(max) NOT NULL,
CONSTRAINT [PK_Project_Notes] PRIMARY KEY ([ProjectId], [Id]),
CONSTRAINT [FK_Project_Notes_Project_ProjectId] FOREIGN KEY ([ProjectId]) REFERENCES [Project] ([Id]) ON DELETE CASCADE
);