private void viewBookAssigned_Load(object sender, EventArgs e)
{
DataTable dt = new DataTable();
dt = lc.getBookCategory();
categorycb.DataSource = dt;
categorycb.ValueMember = dt.Columns[0].ToString();
categorycb.DisplayMember = dt.Columns[1].ToString();
statuscb.Text = "All";
categorycb.Text = "All";
}