the namespace is not recognised

using Microsoft.EntityFrameworkCore;
using FakeFlightBookingApp.Model;
namespace FakeFlightBookingAPI.Data
{
    public class ApplicationDbContext : DbContext
    {
        public ApplicationDbContext(DbContextOptions<ApplicationDbContext> options) : base(options) { }


        public DbSet<Admin> AdminUsers { get; set; }
        public DbSet<Customer> RegularUsers { get; set; }
    }
}