private void CheckInButton_Click(object sender, EventArgs e) { if (InputValidator.IsIntValue(studentNumberTextBox.Text)) { int id = int.Parse(studentNumberTextBox.Text); if (studentManager.IsCheckedIn(id)) { var s = studentManager.GetStudent(id); attendanceManager.UpdateDate(id); MessageBox.Show($"Welcome back {s.FirstName}, this is visit number {s.TotalCheckIns}!", "Checked-in"); } else { MessageBox.Show("Could not find this student number. Register or try again.", "Invalid Input"); } studentNumberTextBox.Text = ""; } else { MessageBox.Show("Please input your student number or register.", "Invalid Input"); } }