SamusevWinApp/Form1.cs

using Microsoft.EntityFrameworkCore;
namespace samusev_42
{
    public partial class Form1 : Form
    {
        Ispr2522SamusevOvLazarev2Context context;
        public Form1()
        {
            InitializeComponent();
            /// ïðè ñîçäàíèè çàïèñè - îíà íå íà÷èíàåòñÿ ñ 0 è íå ëîìàåòñÿ
            dataGridView1.AllowUserToAddRows = false;

            dataGridView1.DataError += (s, e) => {
                MessageBox.Show("Îøèáêà ôîðìàòà äàííûõ! Ïðîâåðüòå, ÷òî â ÷èñëîâûå ïîëÿ íå ââåäåíû áóêâû.",
                                "Îøèáêà ââîäà", MessageBoxButtons.OK, MessageBoxIcon.Warning);
                e.ThrowException = false;
            };

            dataGridView1.EditMode = DataGridViewEditMode.EditProgrammatically;
        }

       
        protected override void OnLoad(EventArgs e)
        {
            base.OnLoad(e);
            context = new Ispr2522SamusevOvLazarev2Context();
            context.Products.Include(x => x.IdCategoryNavigation).Load();
            context.Products.Include(x => x.IdManufacturerNavigation).Load();
            context.Products.Include(x => x.IdProductNameNavigation).Load();
            context.Products.Include(x => x.IdSupplierNavigation).Load();
            context.Categories.Load();
            context.Manufacturers.Load();
            context.Database.EnsureCreated();
            bindingSource1.DataSource = context.Products.Local.ToBindingList();
            categorySource.DataSource = context.Categories.Local.ToBindingList();
            manufacturerSource.DataSource = context.Manufacturers.Local.ToBindingList();
            product_nameSource.DataSource = context.ProductNames.Local.ToBindingList();
            SupplierSource.DataSource = context.Suppliers.Local.ToBindingList();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            context.SaveChanges();
            dataGridView1.Refresh();
        }

        private void button2_Click(object sender, EventArgs e)
        {
            if (bindingSource1.Current == null) return;
            var form = new EditForm();
            form.categoryBindingSource.DataSource = categorySource.DataSource;
            form.manufacturerBindingSource.DataSource = manufacturerSource.DataSource;
            form.productNameBindingSource.DataSource = product_nameSource.DataSource;
            form.supplierBindingSource.DataSource = SupplierSource.DataSource;
            form.productBindingSource.DataSource = bindingSource1.Current;
            if (form.ShowDialog() == DialogResult.OK)
            {
                bindingSource1.EndEdit();
                context.SaveChanges();
                dataGridView1.Refresh();
            }
        }

        private void SaveEditButton_Click(object sender, EventArgs e)
        {
            context.SaveChanges();
            dataGridView1.Refresh();
        }

        private void buttonDelete_Click(object sender, EventArgs e)
        {
            bindingSource1.RemoveCurrent();
            context.SaveChanges();
            dataGridView1.Refresh();
        }
        /// âàëèäàöèÿ + çàïîëíåíèå êîìáîáîêñîâ è òåêñòáîêñîâ ÷òîáû íå áûëî îøèáêè null
        private void buttonAdd_Click_1(object sender, EventArgs e)
        {
            var newProduct = new Product();
            newProduct.Article = "";
            newProduct.Unit = "øò.";
            newProduct.Description = "-";
            newProduct.Photo = "";
            newProduct.Price = 0;
            newProduct.Count = 0;
            newProduct.Discount = 0;

            var form = new EditForm();
            form.categoryBindingSource.DataSource = categorySource;
            form.manufacturerBindingSource.DataSource = manufacturerSource;
            form.productNameBindingSource.DataSource = product_nameSource;
            form.supplierBindingSource.DataSource = SupplierSource;
            form.productBindingSource.DataSource = newProduct;
            if (form.ShowDialog() == DialogResult.OK)
            {
                try
                {
                    if (newProduct.IdProductName <= 0)
                        throw new System.ComponentModel.DataAnnotations.ValidationException("Âûáåðèòå íàçâàíèå òîâàðà!");
                    if (string.IsNullOrWhiteSpace(newProduct.Article))
                        throw new System.ComponentModel.DataAnnotations.ValidationException("Àðòèêóë íå ìîæåò áûòü ïóñòûì!");
                    if (newProduct.Price < 0)
                        throw new System.ComponentModel.DataAnnotations.ValidationException("Öåíà íå ìîæåò áûòü îòðèöàòåëüíîé!");

                    context.Products.Add(newProduct);
                    context.SaveChanges();
                    bindingSource1.DataSource = context.Products.Local.ToBindingList();
                    dataGridView1.Refresh();
                    MessageBox.Show("Äàííûå óñïåøíî ñîõðàíåíû â áàçó!");
                }
                catch (System.ComponentModel.DataAnnotations.ValidationException valEx)
                {
                    MessageBox.Show(valEx.Message, "Âíèìàíèå", MessageBoxButtons.OK, MessageBoxIcon.Warning);
                }
                catch (Exception ex)
                {
                    string inner = ex.InnerException?.Message ?? ex.Message;
                    MessageBox.Show($"Îøèáêà ÁÄ: {inner}");
                    context.Entry(newProduct).State = EntityState.Detached;
                }
            }
        }
    }
}