ProjectGrid/Data/DataAccessContext.cs

using System.Collections.Generic;
using System.Linq;

using Microsoft.EntityFrameworkCore;
using ProjectGrid.Models;


namespace ProjectGrid.Data
{
    public class DataAccessContext : DbContext, IUserRepository
    {
        private static DataAccessContext _instance;
        public static DataAccessContext GetInstance() => _instance;

        public DataAccessContext(DbContextOptions<DataAccessContext> options) : base(options)
        {
            _instance = this;
        }

        public DbSet<UserData> Users { get; set; }

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.Entity<UserData>().ToTable("USER");
        }

        public IEnumerable<UserModel> GetAll()
        {
            return Users.Select<UserData, UserModel>( data => data.ToModel() );
        }

        public UserModel Add(UserModel user)
        {
            // TODO: check if exist
            Users.Add(new UserData(user));
            SaveChanges();
            return user;
        }
    }

    public class UserData
    {
        public int? Id { get; set; }
        public string Name1 { get; set; }
        public string Name2 { get; set; }
        public string Email { get; set; }

        public UserData() { }
        public UserData(UserModel model)
        {
            Name1 = model.firstName;
            Name2 = model.lastName;
            Email = model.email;
        }

        public UserModel ToModel()
        {
            return new UserModel {firstName = Name1, lastName = Name2, email = Email};
        }
    }
}