Nov2611/EditProduct.cs

using MySql.Data.MySqlClient;
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Diagnostics;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Xml.Linq;
using static System.Windows.Forms.VisualStyles.VisualStyleElement;

namespace NeshinaPolina07_11
{
    public partial class EditProduct : Form
    {
        private readonly int _productId;
        private readonly MySqlConnection _connection;
        public EditProduct(int productId)
        {
            InitializeComponent();
            _productId = productId; 
            _connection = DB.GetInstance().GetConnection();
            LoadComboBoxes();
            LoadProductData();
        }

        private void LoadComboBoxes()
        {
            LoadComboBox("categories", "category_id", "category_name", cmbCategory);
            LoadComboBox("manufacturers", "manufacturer_id", "manufacturer_name", cmbManufacturer);
            LoadComboBox("suppliers", "supplier_id", "supplier_name", cmbSupplier);
        }

        private void LoadComboBox(string table, string idColumn, string nameColumn, System.Windows.Forms.ComboBox combo)
        {
            string query = $"SELECT {idColumn}, {nameColumn} FROM {table} ORDER BY {nameColumn}";
            using (var cmd = new MySqlCommand(query, _connection))
            using (var adapter = new MySqlDataAdapter(cmd))
            {
                var dt = new DataTable();
                adapter.Fill(dt);
                combo.DataSource = dt;
                combo.DisplayMember = nameColumn;
                combo.ValueMember = idColumn;
                combo.SelectedIndex = -1;
            }
        }

        private void LoadProductData()
        {
            string query = @"
                SELECT 
                    product_article, product_name, price, discount,
                    quantity_in_stock, description,
                    category_id, manufacturer_id, supplier_id
                FROM products 
                WHERE product_id = @id";

            using (var cmd = new MySqlCommand(query, _connection))
            {
                cmd.Parameters.AddWithValue("@id", _productId);

                using (var reader = cmd.ExecuteReader())
                {
                    if (reader.Read())
                    {
                        textBox1.Text = reader["product_article"].ToString();    
                        textBox2.Text = reader["product_name"].ToString();        
                        textBox3.Text = reader["price"].ToString();            
                        textBox4.Text = reader["discount"].ToString();            
                        textBox5.Text = reader["quantity_in_stock"].ToString();   
                        textBox6.Text = reader["description"].ToString();         

                        SetComboBoxValue(cmbCategory, reader["category_id"]);
                        SetComboBoxValue(cmbManufacturer, reader["manufacturer_id"]);
                        SetComboBoxValue(cmbSupplier, reader["supplier_id"]);
                    }
                    else
                    {
                        MessageBox.Show("Продукт не найден.", "Ошибка", MessageBoxButtons.OK, MessageBoxIcon.Error);
                        DialogResult = DialogResult.Cancel;
                        Close();
                    }
                }
            }
        }


        private void SetComboBoxValue(System.Windows.Forms.ComboBox combo, object value)
        {
            if (value != DBNull.Value && combo.DataSource != null)
            {
                foreach (DataRowView row in combo.Items)
                {
                    if (row[combo.ValueMember].Equals(value))
                    {
                        combo.SelectedItem = row;
                        return;
                    }
                }
            }
        }

        private void EditProduct_Load(object sender, EventArgs e)
        {

        }

        private void textBox1_TextChanged(object sender, EventArgs e)
        {

        }

        private void button1_Click(object sender, EventArgs e)
        {
            if (!decimal.TryParse(textBox3.Text, out decimal price) || price < 0)
            {
                MessageBox.Show("Цена должна быть числом >= 0.", "Ошибка", MessageBoxButtons.OK, MessageBoxIcon.Error);
                return;
            }

            if (!int.TryParse(textBox4.Text, out int discount) || discount < 0 || discount > 100)
            {
                MessageBox.Show("Скидка должна быть от 0 до 100%.", "Ошибка", MessageBoxButtons.OK, MessageBoxIcon.Error);
                return;
            }

            if (!int.TryParse(textBox5.Text, out int quantity) || quantity < 0)
            {
                MessageBox.Show("Количество должно быть целым числом >= 0.", "Ошибка", MessageBoxButtons.OK, MessageBoxIcon.Error);
                return;
            }

            string query = @"
                UPDATE products 
                SET 
                    product_article = @article,
                    product_name = @name,
                    unit = 'шт.',  -- ← напрямую в запросе!
                    price = @price,
                    discount = @discount,
                    quantity_in_stock = @quantity,
                    description = @description,
                    category_id = @category_id,
                    manufacturer_id = @manufacturer_id,
                    supplier_id = @supplier_id
                WHERE product_id = @id";

            using (var cmd = new MySqlCommand(query, _connection))
            {
                cmd.Parameters.AddWithValue("@article", textBox1.Text);
                cmd.Parameters.AddWithValue("@name", textBox2.Text);
                cmd.Parameters.AddWithValue("@price", price);
                cmd.Parameters.AddWithValue("@discount", discount);
                cmd.Parameters.AddWithValue("@quantity", quantity);
                cmd.Parameters.AddWithValue("@description", textBox6.Text);
                cmd.Parameters.AddWithValue("@category_id", cmbCategory.SelectedValue ?? DBNull.Value);
                cmd.Parameters.AddWithValue("@manufacturer_id", cmbManufacturer.SelectedValue ?? DBNull.Value);
                cmd.Parameters.AddWithValue("@supplier_id", cmbSupplier.SelectedValue ?? DBNull.Value);
                cmd.Parameters.AddWithValue("@id", _productId);

                cmd.ExecuteNonQuery();
            }

            MessageBox.Show("Данные успешно обновлены.", "Успех", MessageBoxButtons.OK, MessageBoxIcon.Information);
            DialogResult = DialogResult.OK;
            Close();
        }

        private void cmbManufacturer_SelectedIndexChanged(object sender, EventArgs e)
        {

        }

        private void cmbSupplier_SelectedIndexChanged(object sender, EventArgs e)
        {

        }
    }
    
}