Entity Framework 3.1 One-To-Many Insert data

I have Offer and OfferLocation. One offer can have many offer location. While saving offer I also want to save offer locations into offer location table, but I get an error saying:

"Microsoft.EntityFrameworkCore.DbUpdateException: An error occurred while updating the entries. See the inner exception for details.\r\n ---> Microsoft.Data.SqlClient.SqlException (0x80131904): Cannot insert explicit value for identity column in table 'OfferLocation' when IDENTITY_INSERT is set to OFF

Please find code below:

public class Offer
{
    public int Id { get; set; }
    public virtual ICollection<OfferLocation> OfferLocations { get; set; }
    ...

}

public class OfferLocation
{
    public int Id { get; set; }
    public int OfferId { get; set; }

    [ForeignKey("OfferId")]
    public virtual Offer Offer { get; set; }
    ...
}

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
     modelBuilder.Entity<OfferLocation>().HasKey(od => new { od.Id, od.OfferId});
     modelBuilder.Entity<OfferLocation>().HasOne(od => od.Offer).WithMany(od => od.OfferLocations).HasForeignKey(od => od.OfferId);
}


public class OfferRepository : BaseRepository<OfferModel>, IOfferRepository
{
        public OfferRepository(Func<MMADbContext> contexFactory) : base(contexFactory) { }

        public async Task<OfferModel> CreateAsync(OfferModel model)
        {
            var context = ContextFactory();
            var offer = new Offer();
            var offerLocations = new List<OfferLocation>();
           

            context.Add(offer);

            foreach (var location in model.Locations)
            {
                OfferLocation offerLocation = new OfferLocation();
                offerLocation.Id = location.Id;
                offerLocation.Country = location.Country;
                offerLocation.Latitude = location.Latitude;
                offerLocation.Longtitude = location.Longtitude;
                offerLocation.Offer = offer;
                offerLocation.Vicinity = location.Vicinity;

                offerLocations.Add(offerLocation);

            }

            offer.OfferLocations = offerLocations;
            await context.SaveChangesAsync();

            return...
        }
    }
}

I know that the problem has to do with inserting key and/or foreign key, but I know sure how to so solve it. Any help appreciated.

Remove the identiy of the

offerLocation.Id

column on database. You are trying to set an Identity to a primary key but you are not allowed to do it.