private void btnMauDeThi_Click(object sender, EventArgs e)
{
this.Hide();
MauDeThi t = new MauDeThi();
t.ShowDialog();
this.Show();
}
private void btnXem_Click(object sender, EventArgs e)
{
r = dataGridView1.CurrentCell.RowIndex;
this.Hide();
MauDeThi t = new MauDeThi(tk, mk, quyen, dataGridView1.Rows[r].Cells[1].Value.ToString());
t.ShowDialog();
this.Show();
}