ReportTable

using Npgsql;
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Data.SqlClient;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace WindowsFormsApp2
{
    public partial class ReportTable : Form
    {
        NpgsqlConnection con;
        int clientID;
        private void Update()
        {

            DataSet ds = new DataSet();
            DataTable dt = new DataTable();
            SqlDataReader dr;
            NpgsqlDataAdapter da;
            string sql = "Select * from clients";
            da = new NpgsqlDataAdapter(sql, con);
            ds.Reset();
            da.Fill(ds);
            dt = ds.Tables[0];
            comboBoxClientName.DataSource = dt;
            comboBoxClientName.DisplayMember = "name";
            comboBoxClientName.ValueMember = "clientID";
            //comboBoxClientName.SelectedValue = clientID.ToString();
            UpdateorderEntries();

        }
        private void UpdateorderEntries()
        {

            DataSet ds = new DataSet();
            DataTable dt = new DataTable();
            SqlDataReader dr;
            NpgsqlDataAdapter da;
            string sqlorderEntries = "SELECT orders.orderID, goods.name, price*amount AS cost FROM orders LEFT JOIN orderEntries ON orders.clientID = :clientID AND orderEntries.orderID = orders.orderID JOIN goods ON goods.goodID = orderEntries.goodID WHERE delivered = false";
            NpgsqlCommand command = new NpgsqlCommand(sqlorderEntries, con);
            command.Parameters.AddWithValue("clientID", comboBoxClientName.SelectedValue);
            da = new NpgsqlDataAdapter(command);
            ds.Reset();
            da.Fill(ds);
            dt = ds.Tables[0];
            dataGridView1.DataSource = dt;
        }
        public ReportTable()
        {
            InitializeComponent();
            con = new NpgsqlConnection("Server=localhost;Port=5432;User Id=postgres;Password=masterkey;Database=lemmaITDB");
            con.Open();

        }

        private void ReportTable_Load(object sender, EventArgs e)
        {
            Update();
        }

        private void ReportTable_FormClosed(object sender, FormClosedEventArgs e)
        {

        }

        private void comboBoxClientName_SelectedIndexChanged(object sender, EventArgs e)
        {
            Update();
        }
    }
}