//кнопка добавления объекта Inspection в таблицу InspectionTableForm
        private void btnAdd_Click(object sender, EventArgs e)
        {
            InspectionForm frmIns = new InspectionForm();
            DialogResult   result = frmIns.ShowDialog(this);

            if (result == DialogResult.Cancel)
            {
                return;
            }

            Inspection inspection = new Inspection();

            List <Car> cars = db.Cars.ToList();

            for (int i = 0; i < cars.Count; i++)
            {
                if (cars[i].Id == MainForm.Global_SelectRowMainForm)
                {
                    addCar = cars[i];
                    break;
                }
            }

            inspection.DateInspection   = frmIns.dateTimePickerDateInspection.Text;
            inspection.NumberInspection = Convert.ToInt32(frmIns.textBoxNumberInspection.Text);
            inspection.Car = (Car)addCar;

            db.Inspections.Add(inspection);
            db.SaveChanges();

            //рефреш, запускается только после добавления второго экземпляра
            dataGridViewInspectionTableForm.DataSource = db.Inspections.Where(p => p.CarId == MainForm.Global_SelectRowMainForm).ToList(); // обновляем грид
            MessageBox.Show("Объект обновлен");
        }
        //кнопка редактирования выбранного объекта Inspection в таблице InspectionTableForm
        private void btnEdit_Click(object sender, EventArgs e)
        {
            if (dataGridViewInspectionTableForm.SelectedRows.Count > 0)
            {
                int  index     = dataGridViewInspectionTableForm.SelectedRows[0].Index;
                int  id        = 0;
                bool converted = Int32.TryParse(dataGridViewInspectionTableForm[0, index].Value.ToString(), out id);
                if (converted == false)
                {
                    return;
                }

                Inspection inspection = db.Inspections.Find(id);

                InspectionForm frmIns = new InspectionForm();
                frmIns.dateTimePickerDateInspection.Text = inspection.DateInspection;
                frmIns.textBoxNumberInspection.Text      = Convert.ToString(inspection.NumberInspection);


                List <Car> cars = db.Cars.ToList();

                if (inspection.Car != null)
                {
                    for (int i = 0; i < cars.Count; i++)
                    {
                        if (cars[i].Id == MainForm.Global_SelectRowMainForm)
                        {
                            addCar = cars[i];
                            break;
                        }
                    }
                }
                addCar.Id = inspection.Car.Id;

                DialogResult result = frmIns.ShowDialog(this);

                if (result == DialogResult.Cancel)
                {
                    return;
                }

                inspection.DateInspection   = frmIns.dateTimePickerDateInspection.Text;
                inspection.NumberInspection = Convert.ToInt32(frmIns.textBoxNumberInspection.Text);

                inspection.Car = (Car)addCar;

                db.Entry(inspection).State = EntityState.Modified;
                db.SaveChanges();

                dataGridViewInspectionTableForm.DataSource = db.Inspections.Where(p => p.CarId == MainForm.Global_SelectRowMainForm).ToList(); // обновляем грид
                MessageBox.Show("Объект обновлен");
            }
        }