private void sinhViênToolStripMenuItem_Click(object sender, EventArgs e)
{
Khoa_Lop frm2 = new Khoa_Lop();
frm2.MdiParent = this;
frm2.Show();
}
private void button4_Click(object sender, EventArgs e)
{
this.Close();
Khoa_Lop frm = new Khoa_Lop();
frm.Show();
}
