่ช่วยดูโค้ด C# ที่เชื่อมต่อกับฐานข้อมูล sql ให้หน่อยค่ะ

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Data.SqlClient;
using System.Data.Sql;
using System.Data.SqlTypes;
using System.IO;
using System.Drawing.Printing;
using Microsoft.VisualBasic;


namespace WinFormSheet28
{
    public partial class Form2 : Form
    {
        public Form2()

       { 
            InitializeComponent();
        }

        private void Form2_Load(object sender, EventArgs e)
        {

            this.orderTableAdapter.Fill(this.lab2DataSet1order.order);
       
            this.productTableAdapter.Fill(this.lab2DataSetproduct.Product);

            DB.connectionString = @"Data Source=DESKTOP-E3U2G8E;Initial Catalog=lab2;Integrated Security=True";

            int[] amount = new int[13];
            int[] num = new int[13];
            listView1.Columns.Add("เลขที่ใบสั่ง", 80, HorizontalAlignment.Center);
            listView1.Columns.Add("รหัสสินค้า", 80, HorizontalAlignment.Center);
            listView1.Columns.Add("ชื่อสินค้า", 100, HorizontalAlignment.Center);
            listView1.Columns.Add("จำนวน", 80, HorizontalAlignment.Center);
            listView1.Columns.Add("ราคา", 80, HorizontalAlignment.Center);
            listView1.Columns.Add("รวมเป็นเงิน", 80, HorizontalAlignment.Center);
            listView1.Columns.Add("วันที่สั่ง", 80, HorizontalAlignment.Center);
            listView1.View = View.Details;
            listView1.GridLines = true;
            listView1.FullRowSelect = true;
                  
            SqlConnection conn = new SqlConnection(@"Data Source=DESKTOP-E3U2G8ES;Initial Catalog=lab2;Integrated Security=True");
            dateTimepicker1.Enabled = false;

        }
        public void show()
        {
            string sql = "select *from order";
            dataGridView2.DataSource = DB.ExcecuteQuery(sql);
        }

        private void ButtonSave_Click(object sender, EventArgs e)
        {
            
            SqlConnection conn = new SqlConnection(@"Data Source=DESKTOP-E3U2G8E;Initial Catalog=lab2;Integrated Security=True");

            for (int j = 0; j <= listView1.Items.Count - 1; j++)
            {
                string query = @"INSERT INTO order (order_id,pro_id,pro_name,amount,money,total,dateorder) 
                                VALUES(@order_id,@pro_id,@pro_name,@amount,@money,@total,@dateorder)";

                List<SqlParameter> sqlParams = new List<SqlParameter>();
                sqlParams.Add(new SqlParameter("@order_id", txtID.Text));
                sqlParams.Add(new SqlParameter("@pro_id", listView1.Items[j].SubItems[0].Text));
                sqlParams.Add(new SqlParameter("@pro_name", listView1.Items[j].SubItems[1].Text));
                sqlParams.Add(new SqlParameter("@amount", listView1.Items[j].SubItems[2].Text));
                sqlParams.Add(new SqlParameter("@money", listView1.Items[j].SubItems[3].Text));
                sqlParams.Add(new SqlParameter("@total", listView1.Items[j].SubItems[4].Text));
                sqlParams.Add(new SqlParameter("@dateorder", listView1.Items[j].SubItems[5].Text));



                if (DB.ExecuteNonQuery(query, sqlParams))
                {
                    MessageBox.Show("คำสั่งซื้อเสร็จสิ้น");
                    show();

                }
                else
                {
                    MessageBox.Show("เกิดข้อผิดพลาด ไม่สามารถสั่งสินค้าได้", "เกิดข้อผิดพลาด", MessageBoxButtons.OK, MessageBoxIcon.Error);
                }
            }


        }
        private void MaxID()
        {
            int maxId = 0;
      
            string sql = @"SELECT MAX(order_id) FROM order";
            dataGridView2.DataSource = DB.ExcecuteQuery(sql);
            //ClassConnection.DataReader = ClassConnection.Command.ExecuteReader();
            try
            {
               
                
            }
            catch (Exception ex)
            {
                maxId = 0;
            }
            txtID.Text = (maxId + 1).ToString("000");
            textBox1.Text = txtID.Text;
        }
        
    
        private void ButtonAdd_Click(object sender, EventArgs e)
        {
           int i = 0;
            ListViewItem lvi;
            int tmpProductID = 0;
            string amountif = dataGridView1.CurrentRow.Cells[2].Value.ToString();

            if (int.Parse(txtProQty.Text) <= int.Parse(amountif))
            {
                for (i = 0; i <= listView1.Items.Count - 1; i++)
                {
                    tmpProductID = int.Parse(listView1.Items[i].SubItems[0].Text);
                    if (int.Parse(txtProID.Text.Trim()) == tmpProductID)
                    {
                        MessageBox.Show("รหัสสินค้าซ้ำกัน!");
                        txtProID.Focus();
                        return;
                    }
                }
            }
            string[] anydata;
            anydata = new string[]
            {  txtID.Text,
                txtProID.Text,
                txtProName.Text,
                txtProQty.Text,
                txtProPrice.Text,        
                txtTotal.Text,
                dateTimepicker1.Text
                     
            };
            lvi = new ListViewItem(anydata);
            listView1.Items.Add(lvi);


            allsumcal();
            amountallsumcal();
  

        }

        private void allsumcal()
        {
            int i = 0;
            double tmptotal = 0;
            for (i = 0; i <= listView1.Items.Count - 1; i++)
            {
                tmptotal += double.Parse(listView1.Items[i].SubItems[4].Text);
            }

            lblTotal.Text = tmptotal.ToString("#,##0.00");
        }
        private void amountallsumcal()
        {
            int i = 0;
            int tmptotal = 0;
            for (i = 0; i <= listView1.Items.Count - 1; i++)
            {
                tmptotal += int.Parse(listView1.Items[i].SubItems[3].Text);
            }

            txt.Text = tmptotal.ToString("#,##");
        }


        private void EnabledTrue()
        {
            dateTimepicker1.Enabled = true;
            txtProID.Enabled = true;
            txtProQty.Enabled = true;
            listView1.Enabled = true;
            
            MaxID();

        }

        private void EnabledFalse()
        {
            dateTimepicker1.Enabled = false;
            txtProID.Enabled = false;
            txtProQty.Enabled = false;
            listView1.Enabled = false;
           
            MaxID();    
        }


  
        private void calamount()
        {
            double total;
            total = (double.Parse(txtProPrice.Text)) * (double.Parse(txtProQty.Text));
            txtTotal.Text = total.ToString("#,##0.00");


        }


        private void txtTotal_TextChanged(object sender, EventArgs e)
        {
            calamount();

        }

        private void listView1_MouseDoubleClick(object sender, MouseEventArgs e)
        {
                int i = 0;
                for (i = 0; i <= listView1.SelectedItems.Count - 1; i++)
                {
                    ListViewItem lvi;
                    lvi = listView1.SelectedItems[i];
                    listView1.Items.Remove(lvi);
                }
                
        }

        private void dataGridView1_CellContentClick_1(object sender, DataGridViewCellEventArgs e)
        {
            txtProID.Text = dataGridView1.CurrentRow.Cells[0].Value.ToString();
            txtProName.Text = dataGridView1.CurrentRow.Cells[1].Value.ToString();
            txtProPrice.Text = dataGridView1.CurrentRow.Cells[4].Value.ToString();
        }

        private void txtProQty_TextChanged(object sender, EventArgs e)
        {
            calamount();

        }

        private void txt_TextChanged(object sender, EventArgs e)
        {
            amountallsumcal();
        }

        private void ButtonCancel_Click(object sender, EventArgs e)
        {
            Form f10 = new main();
            f10.Show();
            this.Hide();
 
         }

        }

    }