private void btnAdd_Click(object sender, EventArgs e)
{
// hiển thị form add
SETTING_Teacher2 set_teacher2 = new SETTING_Teacher2(gteacher);
set_teacher2.ShowDialog();
this.Close();
}
private void linkLabel2_LinkClicked(object sender, LinkLabelLinkClickedEventArgs e)
{
// giải phóng bộ nhớ
DeletePanel();
set_teacher2 = new SETTING_Teacher2(gTeacher);
set_teacher2.ShowDialog();
}