Insert value into identity column in Core 2.2 - entity-framework-core

Question

Trying to seed database in MSSQL server. 'Id' column is set to identity. I fail to understand why EF needs data for 'Id:
public class Location
{
public int? Id { get; set; }
public string Name { get; set; }
public IList<Office> Offices { get; set; }
}
... fluent API:
modelBuilder.Entity<Location>()
.HasKey(k => k.Id);
modelBuilder.Entity<Location>()
.Property(p => p.Id)
.UseSqlServerIdentityColumn()
.ValueGeneratedOnAdd();
modelBuilder.Entity<Location>()
.HasData(
new Location() { Name = "Sydney" },
new Location() { Name = "Melbourne" },
new Location() { Name = "Brisbane" }
);
... as far as I understand 'Id' doesn't need to be provided if it's generated by server on insert. Why do I get the messages about not providing Id ...

Answer 1

I think that the error is here
public int? Id { get; set; }
Id should not be nullable.
Update:
What I mean is that you should write:
public int Id { get; set; }
The question mark makes your property nullable, but since it is a primary key it cannot be null.
I did a littel example here:
using System.Collections.Generic;
namespace ConsoleApp2.Models
{
public class Location
{
public int Id { get; set; }
public string Name { get; set; }
public IList<Office> Offices { get; set; }
}
}
Fluent Api
migrationBuilder.CreateTable(
name: "Locations",
columns: table => new
{
Id = table.Column<int>(nullable: false)
.Annotation("SqlServer:ValueGenerationStrategy", SqlServerValueGenerationStrategy.IdentityColumn),
Name = table.Column<string>(nullable: true)
},
constraints: table =>
{
table.PrimaryKey("PK_Locations", x => x.Id);
});
I can add new location without problems.
using ConsoleApp2.Models;
using System.Collections.Generic;
namespace ConsoleApp2
{
class Program
{
static void Main(string[] args)
{
MyDbContext _c = new MyDbContext();
List<Office> list = new List<Office>()
{
new Office()
{
OfficeName = "Reception"
}
};
Location l = new Location()
{
Name = "New York",
Offices = list
};
_c.Locations.Add(l);
_c.SaveChanges();
}
}
}
Im using .net core 2.1 with EFcore 2.2.2.
I hope that help.