Question

I’m retrieving data from another database that has already created unique IDs for each “beer” entity. However, when I assign the unique key value from the remote database to a new “beer” object, it gets replaced as soon as the object is inserted into the database.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.ComponentModel.DataAnnotations;
using BeerRecommender.Models.ViewModels;

namespace BeerRecommender.Models
{
    public class Beer
    {
        public Beer()
        {
            Created = DateTime.Now;
            Updated = DateTime.Now;
        }

    [Key]
    public int ID { get; set; }

    public string Name { get; set; }

    public string Description { get; set; }

    public Brewery Brewery { get; set; }

    public DateTime Created { get; set; }

    public DateTime Updated { get; set; }

    public ICollection<City> Cities { get; set; }

    public ICollection<Tag> Tags { get; set; }

    public Style Style { get; set; }
    }
}

I’m using the UnitOfWork pattern.

UnitOfWork.BeerRepository.Insert(beer);
UnitOfWork.Save();

Answer 1

As you already discovered, EF will generate values for int primary keys. To fine tune this behavior you need to mark your key with the DatabaseGenerated attribute (or you can also configure this with the the fluent api‘s HasDatabaseGeneratedOption method):

    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.None)]
    public int ID { get; set; }