private void Add_btn_Click(object sender, EventArgs e) { // get values from text boxes if they were inserted by user string username = username_textbox.ForeColor == Color.Black ? username_textbox.Text : ""; string email = email_textbox.ForeColor == Color.Black ? email_textbox.Text : ""; string fname = firstname_textbox.ForeColor == Color.Black ? firstname_textbox.Text : ""; string mname = middlename_textbox.ForeColor == Color.Black ? middlename_textbox.Text : ""; string lname = lastname_textbox.ForeColor == Color.Black ? lastname_textbox.Text : ""; string cardNo = cardnumber_textbox.ForeColor == Color.Black ? cardnumber_textbox.Text : ""; int periodicity = DB_API.SelectRecurenceIdbyDesignation((string)Periodicity_comboBox.SelectedItem); DateTime term = DateTime.Parse(term_dateTimePicker.Value.ToString()); // verify if email field is filled if (email.Equals("")) { ErrorMessenger.EmptyField("Email"); return; } // verify that all mandatory fields are filled (if subscripition is checked) if (active_checkBox.Checked) { if ("".Equals(fname) || "".Equals(lname) || "".Equals(cardNo) || "".Equals(periodicity)) { ErrorMessenger.EmptyField("Every field marked (*)"); return; } } // verify if user exists, if so, cannot be added, only updated var exists = DB_API.ExistsUser(email); if (exists) { ErrorMessenger.Error("User already exists!"); return; } // add user DB_API.InsertUser(username, email, fname, mname, lname, cardNo, periodicity, term, active_checkBox.Checked); // upadte listBox with new user PopulateUsersListView(); }