entity framework multiple relationships - ef-code-first

Question

I'm new to Entity Framework and I have probably a simple question.
I have simplified the structure at a maximum to be clear (I hope I am).
Imagine that I just need to create a simple "Enterprise" class, with only a Name.
Then another class named "Worker" with also just a Name for the worker.
A worker should belong to an Enterprise.
An Enterprise must have a manager (who is a Worker).
So here is how I imagine these simple classes :
public class Worker
{
public int WorkerId { get; set; }
public String Name { get; set; }
public int EnterpriseId { get; set; } // ForeignKey for Enterprise
public Enterprise Enterprise { get; set; }
}
public class Enterprise
{
public int EnterpriseId { get; set; }
public String Name { get; set; }
public Worker Manager { get; set; }
public List<Worker> Workers { get; set; }
}
I'd like these classes to result in the following DB structure :
Table Worker
WorkerId (PK, int, not null)
Name (varchar(128), not null)
EnterpriseId (FK, int)
Table Enterprise
EnterpriseId (PK, int, not null)
Name (varchar(128), not null)
Manager (FK, int)
I tried many things with modelBuilder, but I never obtain what I want.
Is there a solution with Fluent API to do what I want to do?
Thank you very much for your help.

Answer 1

This will not get you what you want (in Db) - but is what I recommend...
public ICollection<Worker> Workers { get; set; } // instead of List<>
// ...
modelBuilder.Entity<Worker>()
.HasRequired(x => x.Enterprise)
.WithMany(x => x.Workers)
.HasForeignKey(x => x.EnterpriseId)
.WillCascadeOnDelete(false);
modelBuilder.Entity<Enterprise>()
.HasOptional(x => x.Manager)
.WithOptionalPrincipal() // x => x.DefaultForEntity)
.WillCascadeOnDelete(false);
You can use it like:
var enterprise = new Enterprise { Manager = new Worker { Name = "Manager", }, };
enterprise.Workers = new[]
{
enterprise.Manager,
new Worker{ Name = "Worker1", },
new Worker{ Name = "Worker2", },
new Worker{ Name = "Worker3", },
new Worker{ Name = "Worker4", },
new Worker{ Name = "Worker5", },
};
db.Enterprises.Add(enterprise);
db.SaveChanges();
var enterprises = db.Enterprises.ToList();
This is exactly what you want...
modelBuilder.Entity<Worker>()
.HasRequired(x => x.Enterprise)
.WithMany(x => x.Workers)
.HasForeignKey(x => x.EnterpriseId)
.WillCascadeOnDelete(false);
modelBuilder.Entity<Enterprise>()
.HasKey(x => x.EnterpriseId);
modelBuilder.Entity<Enterprise>()
.HasOptional(x => x.Manager)
.WithOptionalDependent() // x => x.DefaultForEntity)
.WillCascadeOnDelete(false);
...but will not work - due to cyclical references (EF error).
Here is a pretty detailed example for a similar / identical solution...
Entity Framework One-to-Many with Default

Answer 2

I don't know how you intend to get the manager object, but my guess is you need to use Inheritance to make your design optimal. Try this:
public abstract class Employee
{
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int EmployeeId{ get; set; }
public String Name { get; set; }
[ForeignKey("Enterprise"), DatabaseGenerated(DatabaseGeneratedOption.None)]
public int EnterpriseId { get; set; } // ForeignKey for Enterprise
public Enterprise Enterprise { get; set; }
}
[Table("Workers")] // Table per Type (TPT), This will be your Table name in your database
public class Worker : Employee
{
//Add properties only related to workers
}
[Table("Managers")] // Table per Type (TPT). This will be your Table name in your database
public class Manager : Employee
{
//Add properties only related to Managers
}
public class Enterprise
{
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int EnterpriseId { get; set; }
public String Name { get; set; }
public virtual ICollection<Employee> Employees{ get; set; }
}
Note: Sorry this is done using Property Mapping
Link: Here is a link to simple Fluent Mapping example
Link : Read about Table per Type (TPT) Inheritance here