HOW TO fill installment dropdown list

ds1 = objcheck.CheckPaidInstallment();
if (ds1.Tables.Count > 0)
{
ddlInstallment.DataSource = ds1;
ddlInstallment.DataTextField = ds1.Tables[0].Columns["PaymentType"].ColumnName.ToString();
ddlInstallment.DataValueField = ds1.Tables[0].Columns["PaymentID"].ColumnName.ToString();
ddlInstallment.DataBind();
ddlInstallment.Items.Insert(0, "--Select--");
}