Primary key stays null after inserting Entity with Entity Framework

Question

I want to insert a new entry into my database with the following commands:

Repository<Fueltype, TankeeContext> repository = new Repository<Fueltype, TankeeContext>();
Fueltype fuel = new Fueltype() {
    Name = "Strom"
};
repository.Create(fuel);

That is the create- method of the repository

 public void Create(T entity)
 {
     using (Ctx db = new Ctx())
      {
         db.Set<T>().Add(entity);
         db.SaveChanges();
      }
 }

My problem is, that after inserting the entity Fueltype and calling the SaveChanges() method, the ID (IdFuelType) stays null, although it should be updated by the entity framework. My Entity Fueltype looks like that:

public partial class Fueltype
    {
        public Fueltype()
        {
            Gasprice = new HashSet<Gasprice>();
        }

        [DatabaseGenerated(DatabaseGeneratedOption.None)]
        public int IdFuelType { get; set; }
        public string Name { get; set; }

        public ICollection<Gasprice> Gasprice { get; set; }
    }

Because I used Database-First, the entities got created automatically, so I am not quite sure. — romaneso, Oct 30 '17 at 08:52
I would start bij checking that :) By default it's set to false. — Tvt, Oct 30 '17 at 08:54
If it's a primary key it can't be null. Primary keys are non-nullable by definition. — Zohar Peled, Oct 30 '17 at 08:55
@ZoharPeled I am aware of that, my primary key gets updated in the database, so when I call SaveChanges(), the entry gets inserted into the database (for example with id 40), but it doesn't get updated as a entity after calling that method. — romaneso, Oct 30 '17 at 08:57
@Tvt I am using MySQL, so I guess there is no Identity Specification method, or? — romaneso, Oct 30 '17 at 08:59
@romaneso hmm no idea then. I know if you use Model first for example on a newly created table the identity specification will be false and because of that it will not auto increment and leave the value "NULL" — Tvt, Oct 30 '17 at 09:02
@Tvt yeah, I know - that's the first time that .net core and entity framework is doing funny things to me. — romaneso, Oct 30 '17 at 09:04
What does `DatabaseGeneratedOption.None` mean? https://msdn.microsoft.com/en-us/library/system.componentmodel.dataannotations.schema.databasegeneratedoption(v=vs.110).aspx — mjwills, Oct 30 '17 at 09:14
@mjwills that doesn't work when you work by Database First unfortunately. — romaneso, Oct 30 '17 at 09:47
Instead of DatabaseGeneratedOption.None, have you tried DatabaseGeneratedOption.Identity? — Mikkel, Oct 30 '17 at 09:51
Change this line [DatabaseGenerated(DatabaseGeneratedOption.None)] to [DatabaseGenerated(DatabaseGeneratedOption.Identity)] — Sandeep, Oct 30 '17 at 11:49

score 1 · Answer 1 · answered Oct 30 '17 at 11:57

You should set the value of IdFuelType or change this line of code

[DatabaseGenerated(DatabaseGeneratedOption.None)] to

[DatabaseGenerated(DatabaseGeneratedOption.Identity)]

Refer the following link

https://forums.asp.net/t/2080959.aspx?+Errors+DatabaseGenerated+DatabaseGeneratedOption+None+v+Key

Primary key stays null after inserting Entity with Entity Framework

1 Answers1