private void gridView_CellDoubleClick(object sender, DataGridViewCellEventArgs e)
        {
            var invoiceId = (int)gridView.Rows[e.RowIndex].Cells[0].Value;
            var form      = new ViewInvoiceForm(invoiceId)
            {
                MdiParent = this.MdiParent
            };

            form.Show();
        }
        private void FormOnSave(Invoice obj)
        {
            var form = new ViewInvoiceForm(obj.Id)
            {
                MdiParent = this.MdiParent
            };

            form.Show();
            Close();
        }