private void AddItemBtn_Click(object sender, RoutedEventArgs e)
        {
            try
            {
                if (Int32.Parse(AmountUpdate.Text) > 0)
                {
                    DBGetItems db = new DBGetItems();
                    List <Entity.ExtendedItem> item_list = db.GetItems();

                    foreach (ExtendedItem i in item_list)
                    {
                        if (i.name.Equals(Items.SelectedItem.ToString()))
                        {
                            i.amount = Int32.Parse(AmountUpdate.Text);
                            i.UpdateValues();
                            invoice.items.Add(i);
                        }
                    }

                    SetDataGrid();
                }
            }catch (Exception ex)
            {
                Debug.WriteLine(ex.Message);
            }
        }
        private void UpadateItemBtn_Click(object sender, RoutedEventArgs e)
        {
            try
            {
                if (Int32.Parse(AmountUpdate.Text) > 0)
                {
                    DBUpdateInvoice db_update = new DBUpdateInvoice();
                    DBGetItems      db_items  = new DBGetItems();


                    db_update.UpdateItemAmount(invoice, Items.SelectedItem.ToString(), Int32.Parse(AmountUpdate.Text));

                    SetComboboxItem();
                    AmountUpdate.Text = "" + 0;
                }
                else
                {
                    MessageBox.Show("Wypełnij wszystkie pola", "Błąd");
                }
            }
            catch (Exception ex)
            {
                Debug.WriteLine(ex.Message);
                MessageBox.Show("Błędne wypełnienie pól", "Błąd");
            }
        }
        private void AddItemBtn_Click(object sender, RoutedEventArgs e)
        {
            try
            {
                if (Int32.Parse(Amount.Text) > 0)
                {
                    DBUpdateInvoice db_update = new DBUpdateInvoice();
                    DBGetItems      db_items  = new DBGetItems();

                    ExtendedItem chosen_item         = null;
                    List <Entity.ExtendedItem> items = db_items.GetItems();

                    foreach (ExtendedItem i in items)
                    {
                        if (i.name.Equals(AvaiableItems.SelectedItem))
                        {
                            chosen_item        = i;
                            chosen_item.amount = Int32.Parse(Amount.Text);
                        }
                    }

                    if (chosen_item != null)
                    {
                        chosen_item.UpdateValues();
                        invoice.items.Add(chosen_item);
                    }
                    db_update.UpdateItemList(invoice, chosen_item);
                    SetComboboxItem();
                    Amount.Text = "" + 0;
                }
            }catch (Exception ex)
            {
                Debug.WriteLine(ex.Message);
            }
        }
        private void SetComboboxes()
        {
            DBGetSubjects db_subject = new DBGetSubjects();

            SubjectForComboBox.ItemsSource  = db_subject.GetSubjectNames();
            SubjectFromComboBox.ItemsSource = db_subject.GetSubjectNames();



            DBGetItems db_items = new DBGetItems();

            Items.ItemsSource   = db_items.GetItemsNames();
            Items.SelectedIndex = 0;
        }
        private void DeleteItemBtn_Click(object sender, RoutedEventArgs e)
        {
            try
            {
                DBDeleteInvoice db_delete = new DBDeleteInvoice();
                DBGetItems      db_items  = new DBGetItems();

                db_delete.DeleteItemInInvoice(invoice, Items.SelectedItem.ToString());
                SetComboboxItem();
            }
            catch (Exception ex)
            {
                Debug.WriteLine(ex.Message);
            }
        }
        private void SetComboboxes()
        {
            DBGetSubjects db_subject = new DBGetSubjects();

            SubjectForComboBox.ItemsSource  = db_subject.GetSubjectNames();
            SubjectFromComboBox.ItemsSource = db_subject.GetSubjectNames();

            SubjectForComboBox.SelectedItem  = invoice.subject_for.Name;
            SubjectFromComboBox.SelectedItem = invoice.subject_from.Name;

            DBGetItems db_items = new DBGetItems();

            AvaiableItems.ItemsSource   = db_items.GetItemsNames();
            AvaiableItems.SelectedIndex = 0;


            SetComboboxItem();
        }