/// <summary>
        /// Get all bookers from the database
        /// </summary>
        private void GetBookersFromDB()
        {
            Database db = new Database();
            db.CreateCommand("SELECT id,firstname FROM BOOKERS");

            db.OpenConnection();

            db.ExecuteCommand();
            OracleDataReader dr = db.DataReader;

            while (dr.Read())
            {
                Booker booker = new Booker(dr.GetInt16(0), dr.GetString(1));
                BookerList.Add(booker);
                comboBox1.Items.Add(booker.Name);
            }

            db.CloseConnection();
        }
        /// <summary>
        /// check if all fields are filled in
        /// </summary>
        /// <returns>bool</returns>
        private bool authenticateStep2()
        {
            bool boxesFilled = true;
            panel3.Controls.Clear();
            int StartX = 0;
            int StartY = 0;
            for (int i = 0; i < nameErrorLabels.Count; i++)
            {
                nameErrorLabels[i].Visible = false;
            }
            for (int i = 0; i < additionalName.Count; i++)
            {
                if (additionalName[i].Text == "")
                {
                    boxesFilled = false;
                    nameErrorLabels[i].Visible = true;
                }

                Booker boeker = new Booker();
                boeker.Name = additionalName[i].Text;
                boeker.PhoneNumber = additionalPhone[i].Text;
                medeboekers.Add(boeker);
                {
                    Label lbName = new Label();
                    lbName.Text = "Naam";
                    lbName.Location = new Point(StartX, StartY + (i * 25));

                    Label lbPhone = new Label();
                    lbPhone.Text = "Telefoonnummer";
                    lbPhone.Location = new Point(StartX, StartY + (i * 25) + 25);

                    Label lbS4Name = new Label();
                    lbS4Name.AutoSize = true;
                    lbS4Name.Text = boeker.Name;
                    lbS4Name.Location = new Point(StartX + 110, StartY + (i * 25));

                    Label lbS4Phone = new Label();
                    lbS4Phone.AutoSize = true;
                    lbS4Phone.Text = (boeker.PhoneNumber == "") ? "Geen telefoonnummer..." : boeker.PhoneNumber;
                    lbS4Phone.Location = new Point(StartX + 110, StartY + (i * 25) + 25);

                    panel3.Controls.Add(lbName);
                    panel3.Controls.Add(lbPhone);
                    panel3.Controls.Add(lbS4Name);
                    panel3.Controls.Add(lbS4Phone);

                    StartY += 30;
                }
            }
            return boxesFilled;
        }