public ActionResult ShowInvoiceList(string viewName, Models.InvoiceListFilter filter, int? size)
        {
            if (!size.HasValue)
            {
                size = 10;
            }
            int count = 0;
            var list = SalesService.GetInvoiceList(User.GetUserPrincipal().CurrentUser, filter, 0, size.Value, out count);

            var model = new Models.InvoiceList(list);
            model.ItemCount = count;
            model.PageIndex = 0;
            model.PageSize = size.Value;

            ViewData.Model = model;
            return PartialView(viewName);
        }
        public ActionResult Index(Models.InvoiceListFilter filter, int? page, int? size)
        {
            var pageId = GetPageId(page);

            if (!size.HasValue)
            {
                size = 10;
            }

            int count = 0;
            var list = SalesService.GetInvoiceList(User.GetUserPrincipal().CurrentUser, filter, pageId, size.Value, out count);

            var model = new Models.InvoiceList(list);
            model.ItemCount = count;
            model.PageIndex = pageId + 1;
            model.PageSize = size.Value;

            ViewData.Model = model;
            return GetDefaultView("invoicelist");
        }