Ekz_LEDNEV/Form1.cs

using MySql.Data.MySqlClient;
using System.Data;

namespace ekz_lednev
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        // Çàãðóçêà ôîðìî÷êè è çàïîëíåíèå äàííûõ â äàòàãðèäâüþ
        private void Form1_Load(object sender, EventArgs e)
        {
            DB dB = DB.GetInstance();
            DataTable dt = new DataTable();
            MySqlDataAdapter adp = new MySqlDataAdapter();
            MySqlCommand cmd = new MySqlCommand($@"
                SELECT b.`id`, b.`name`, bt.`name` AS `material_type_id`, b.`price_one`, b.`quantity_real`, b.`quantity_plan`, b.`quantity_pack`, bu.`name` AS `unit_id`
                FROM `Material` b
                LEFT JOIN `material_type` bt ON bt.`id`=b.`material_type_id`
                LEFT JOIN `unit` bu ON bu.`id`=b.`unit_id`
            ", dB.GetConnection());

            adp.SelectCommand = cmd;
            adp.Fill(dt);
            dataGridView1.DataSource = dt;
        }


        // Êíîïêà óäàëåíèÿ
        private void button3_Click(object sender, EventArgs e)
        {
            DataGridViewRow dtRow = dataGridView1.SelectedRows[0];
            int id = Convert.ToInt32(dtRow.Cells["id"].Value);

            DB dB = DB.GetInstance();
            MySqlCommand cmd = new MySqlCommand($"DELETE FROM `pozorisp_lednev_ekz`.`Material` WHERE (`id` = '{id}');", dB.GetConnection());
            cmd.ExecuteNonQuery();

            MessageBox.Show("Óäàëåíî!");
            Application.Restart();
        }

        // Êíîïêà äîáàâëåíèå
        private void button1_Click(object sender, EventArgs e)
        {
            Form2 form2 = new Form2();
            form2.Show();
        }

        // Êíîïêà ðåäàêòèðîâàíèÿ
        private void button2_Click(object sender, EventArgs e)
        {
            Form3 form3 = new Form3();
            form3.Show();
        }

        // Ïîäñêàçêà
        private void button5_Click(object sender, EventArgs e)
        {
            MessageBox.Show("Äàííàÿ ñòðàíèöà âûâîäèò ñïèñîê òîâàðîâ, ïðè âàøåì æåëàíèè ñäåëàòü ÷òî-ëèáî ñ ýòèì ñïèñêîì, âîñïîëüçóéòåñü êíîïêàìè" +
                "              Äîï. Èíôî - òàáëèöà ñ äîï. èíôîðìàöèåé");
        }

        private void button6_Click(object sender, EventArgs e)
        {
            Form4 form4 = new Form4();
            form4.Show();
        }

        private void button4_Click(object sender, EventArgs e)
        {
            Form5 form5 = new Form5();
            form5.Show();
        }
    }
}