}//FillInvoiceFields

        private void OrderDatePicker_SelectedDateChanged(object sender, SelectionChangedEventArgs e)
        {
            if (invoicesList == null || !DateTime.TryParse(sender.ToString(), out DateTime date))
            {
                return;
            }

            MessageBox.Show(date.ToString());

            using (SmallBusinessDBEntities context = new SmallBusinessDBEntities()) {
                invoicesList = (from i in context.Invoices
                                join s in context.Suppliers on i.supplierID equals s.supplierID
                                where i.date.Day == date.Day &&
                                i.date.Month == date.Month &&
                                i.date.Year == date.Year
                                select new InvoisesTemplate {
                    CompanyName = s.companyName,
                    Date = i.date,
                    EmployeeID = i.employeeID,
                    InvoiceID = i.invoiceID,
                    InvoiceNumber = i.invoiceNumber,
                    Official = i.official,
                    Overhead = i.overhead,
                    Paid = i.paid,
                    PayToDate = i.payToDate,
                    SupplierID = i.supplierID,
                    TotalSumm = (from inv in context.Invoices
                                 join id in context.InvoiceDetails on inv.invoiceID equals id.invoiceID
                                 where inv.invoiceID == i.invoiceID
                                 select new {
                        quantity = id.quantity,
                        price = id.price
                    }).Sum(s => (s.price * s.quantity))
                }).ToList();

                InvoicesDataGrid.ItemsSource   = invoicesList;
                InvoicesDataGrid.SelectedIndex = 0;
                if (InvoicesDataGrid.SelectedIndex != -1)
                {
                    InvoicesDataGrid.Focus();
                }
            }//using
        }
        private void LoadInvoices(DateTime date)
        {
            //date = DateTime.Parse("10.06.2018");

            using (SmallBusinessDBEntities context = new SmallBusinessDBEntities()) {
                invoicesList = (from i in context.Invoices
                                join s in context.Suppliers on i.supplierID equals s.supplierID
                                where i.date.Day == date.Day &&
                                i.date.Month == date.Month &&
                                i.date.Year == date.Year
                                select new InvoisesTemplate {
                    CompanyName = s.companyName,
                    Date = i.date,
                    EmployeeID = i.employeeID,
                    InvoiceID = i.invoiceID,
                    InvoiceNumber = i.invoiceNumber,
                    Official = i.official,
                    Overhead = i.overhead,
                    Paid = i.paid,
                    PayToDate = i.payToDate,
                    SupplierID = i.supplierID,
                    TotalSumm = (from inv in context.Invoices
                                 join id in context.InvoiceDetails on inv.invoiceID equals id.invoiceID
                                 where inv.invoiceID == i.invoiceID
                                 select new {
                        quantity = id.quantity,
                        price = id.price
                    }).Sum(s => (s.price * s.quantity))
                }).ToList();

                InvoicesDataGrid.ItemsSource = invoicesList;
                InvoicesDataGrid.Focus();
                InvoicesDataGrid.SelectedIndex = invoicesList.Count - 1;
                //if (InvoicesDataGrid.SelectedIndex != -1) {
                //    InvoicesDataGrid.Focus();
                //}
            }//using
        }