private void ManageBooks_Load(object sender, EventArgs e)
{
DataTable dt1 = new DataTable();
DataTable dt2 = new DataTable();
DataTable dt3 = new DataTable();
lc.booksPageLoad(out dt1, out dt2, out dt3);
Namecb.DataSource = dt1;
Namecb.ValueMember = dt1.Columns[0].ToString();
Namecb.DisplayMember = dt1.Columns[1].ToString();
categorycb.DataSource = dt2;
categorycb.ValueMember = dt2.Columns[0].ToString();
categorycb.DisplayMember = dt2.Columns[1].ToString();
authorcb.DataSource = dt3;
authorcb.ValueMember = dt3.Columns[0].ToString();
authorcb.DisplayMember = dt3.Columns[1].ToString();
Namecb.Text = "All";
categorycb.Text = "All";
authorcb.Text = "All";
}