public void ddlProduct_SelectedIndexChanged(object sender, EventArgs e) { CustomerENT entCustomer = new CustomerENT(); CustomerBAL balCustomer = new CustomerBAL(); if (ddlProductID.SelectedIndex > 0) { DataTable dt = balCustomer.SelectProductAmount(Convert.ToInt32(ddlProductID.SelectedValue)); if (dt != null && dt.Rows.Count > 0) { foreach (DataRow dr in dt.Rows) { if (!dr["BottlePrice"].Equals(DBNull.Value)) { txtAmount.Text = Convert.ToDecimal(dr["BottlePrice"]).ToString(); } } } } }