private void ad_bql_Click(object sender, EventArgs e)
{
ad_clicked.Location = ad_bql.Location;
BUS.StudentBLL st = new BUS.StudentBLL();
uc_us.ad_dgv_st.DataSource = st.getAllStudents();
uc_db.Hide();
uc_us.Show();
uc_at.Hide();
uc_cs.Hide();
uc_ep.Hide();
uc_al.Hide();
}