public string registarUtilizador(String username, String password)
        {
            if (getUtilizador(username) == false)
            {
                SqlCommand cmd = new SqlCommand("INSERT INTO Utilizador VALUES (@Name, @Passe)");
                cmd.CommandType = CommandType.Text;
                cmd.Connection = MM.conn;
                cmd.Parameters.AddWithValue("@Name", username);
                cmd.Parameters.AddWithValue("@Passe", password);
                //connection.Open();
                cmd.ExecuteNonQuery();
                return "";
            }
            else
            {
                return "Existe um utilizador com esse nome";
            }
        }



        public Utilizador getUtilizador(String username, String password)
        {
            Utilizador u = null;
            SqlCommand sc;
            SqlDataReader dataReader;
            String query = "SELECT * FROM Utilizador WHERE Username = '" + username + "' AND Password = '" + password + "';";

            try
            {
                sc = new SqlCommand(query, MM.conn);
                dataReader = sc.ExecuteReader();

                if (dataReader.Read())
                {
                    u = new Utilizador(dataReader.GetValue(0).ToString(), dataReader.GetValue(1).ToString(), dataReader.GetValue(2).ToString());
                }

                if(u != null)
                {
                    query = "SELECT * FROM Preferencia WHERE Utilizador = " + u.id + "";
                    sc = new SqlCommand(query, MM.conn);
                    dataReader = sc.ExecuteReader();
                    List<String> tags = new List<String>();
                    float preco = 0;
                    int rating = 0;

                    while (dataReader.Read())
                    {
                        if (dataReader.GetValue(2).ToString().Equals("preco"))
                        {
                            preco = float.Parse(dataReader.GetValue(3).ToString());
                        }

                        if (dataReader.GetValue(2).ToString().Equals("rating"))
                        {
                            int.TryParse(dataReader.GetValue(3).ToString(),out rating);
                        }

                        if (dataReader.GetValue(2).ToString().Equals("tags"))
                        {
                            tags.Add(dataReader.GetValue(3).ToString());
                        }

                    }
                    if(tags != null || preco != 0 || rating != 0)
                    {
                        Preferencias p = new Preferencias(rating, preco, tags);
                        u.preferencias = p;
                        u.pref_bool = true;
                    }
                }

            }
            catch (Exception e)
            {
                MessageBox.Show(e.Message);
            }

            return u;
        }

        public bool getUtilizador(String username)
        {
            Utilizador u = null;
            SqlCommand sc;
            SqlDataReader dataReader;
            String query = "SELECT * FROM Utilizador WHERE Username = '" + username + "';";

            try
            {
                sc = new SqlCommand(query, MM.conn);
                dataReader = sc.ExecuteReader();

                if (dataReader.Read())
                {
                    u = new Utilizador(dataReader.GetValue(0).ToString(), dataReader.GetValue(1).ToString(), dataReader.GetValue(2).ToString());
                }
            }catch(Exception e)
            {
                MessageBox.Show(e.Message);
            }
                if (u != null)
                {
                    return true;
                }
                return false;
        }