private void addStudentButton_Click(object sender, EventArgs e)
{
if (studentComboBox.SelectedIndex == -1)
{
MessageBox.Show("You must choose a valid student to add to the group.");
return;
}
Student student = (Student)studentComboBox.SelectedItem;
APIHandler.AddStudentToGroup(student, this.group);
groupStudents.Add(student);
allNonGroupStudents.Remove(student);
}