private void View_Payment_Details_Load(object sender, EventArgs e) { List <PaymentsClass> payment = new List <PaymentsClass>(); Business_Logic bl = new Business_Logic(); //dataGridView1.DataSource = bl.PaymentDetails(); DataTable dt; dt = bl.PaymentDetails(); foreach (DataRow dr in dt.Rows) { payment.Add(new PaymentsClass(dr["StudentId"].ToString(), dr["Amount"].ToString(), dr["Date"].ToString())); //dataGridView1.DataSource = dt; } var query = from pay in payment orderby pay.StudentId select pay; foreach (PaymentsClass a in query) { listBox1.Items.Add(a.ToString()); } }