private void mnuAdd_Click(object sender, EventArgs e) { if (!clsValidation.ValidateComboBox(cmbTeacherID)) { return; } if (!clsValidation.ValidateComboBox(cmbCourseID)) { return; } clsTeacherCourse objTeacherCourse = new clsTeacherCourse(Convert.ToInt32(cmbTeacherID.Text), Convert.ToInt32(cmbCourseID.Text)); if (!objTeacherCourse.Add()) { return; } MessageBox.Show("Teacher-Course record successfully added!"); objTeacherCourse.ViewAll(dgvTeacherCourse); }