//Typ Gateway
    public enum GatewayType
    {
        gtSQL, gtXML
    }

//BaseEntity - vlastnosti společné pro všechny entity
    public class BaseEntity
    {
        public int Id { get; set; }
    }

//Interface pro všechny Gateway
    public interface IGateway<T> where T : BaseEntity
    {
        IEnumerable<T> List { get; }
        bool Add(T entity);
        bool Delete(T entity);
        bool Update(T entity);
        T FindById(int Id);
        IQueryable<T> SearchFor(Expression<Func<T, bool>> predicate);
    }


//Příklad User SQL gateway
    public class UserGateway_SQL : IGateway<User>
    {
        public IEnumerable<User> List
        {
            get
            {
                throw new NotImplementedException();
            }
        }

        public bool Add(User entity)
        {
            throw new NotImplementedException();
        }

        public bool Delete(User entity)
        {
            throw new NotImplementedException();
        }

        public User FindById(int Id)
        {
            throw new NotImplementedException();
        }

        public IQueryable<User> SearchFor(Expression<Func<User, bool>> predicate)
        {
            throw new NotImplementedException();
        }

        public bool Update(User entity)
        {
            throw new NotImplementedException();
        }
    }

//Mapper pro Usera
    public class UserMapper
    {
        private IGateway<User> gateway;

        public UserMapper(GatewayType type)
        {
            if (type == GatewayType.gtXML)
            {
                this.gateway = new UserGateway_XML();
            }
            else if (type == GatewayType.gtSQL)
            {
                this.gateway = new UserGateway_SQL();
            }
        }

        public List<User> getUsers() {
            List<User> users = new List<User>();
            users.AddRange(gateway.List);

            return users;
        }

        public bool insertUser(User user) {
            return gateway.Add(user);
        }
    }

//User model
    public class User : BaseEntity
    {
        public string Name { get; set; }

        public User(int id, string name) {
            this.Id = id;
            this.Name = name;
        }

        public static User newIntance(string name) {
            return new User(-1, name);
        }
    }


//Example
            User user = User.newIntance("Uživatel 1");
            UserMapper userMapper = new UserMapper(GatewayType.gtSQL);  //Předělám na globální proměnnou

            List<User> userList = userMapper.getUsers();