private void btn_TimKiem_Click(object sender, EventArgs e)
        {
            String key = txt_TimKiem.Text;

            if (cb_TimKiemTheo.SelectedItem.ToString() == "Họ tên")
            {
                if (key != null)
                {
                    dgv_BenhNhan.DataSource = bus_benhnhan.FindBenhNhanByName(key);
                    ClearALL();
                }
            }
            else if (cb_TimKiemTheo.SelectedItem.ToString() == "Căn cước công dân")
            {
                if (key != null)
                {
                    dgv_BenhNhan.DataSource = bus_benhnhan.FindBenhNhanByCCCD(key);
                    ClearALL();
                }
            }
            else if (cb_TimKiemTheo.SelectedItem.ToString() == "Địa chỉ")
            {
                if (key != null)
                {
                    dgv_BenhNhan.DataSource = bus_benhnhan.FindBenhNhanByDiaChi(key);
                    ClearALL();
                }
            }
        }
 private void btn_TimKiem_Click(object sender, EventArgs e)
 {
     if (cb_TimKiemTheo.Text == "Họ tên")
     {
         dgv_BenhNhan.DataSource = bus.FindBenhNhanByName(txt_TimKiem.Text);
     }
     else
     {
         dgv_BenhNhan.DataSource = bus.FindBenhNhanByCCCD(txt_TimKiem.Text);
     }
     ClearAll();
 }