public async Task <IActionResult> OnPostAsync(int?id)
        {
            if (id == null)
            {
                return(NotFound());
            }

            InvoiceModel = await _context.InvoiceTable.FindAsync(id);

            if (InvoiceModel != null)
            {
                _context.InvoiceTable.Remove(InvoiceModel);
                await _context.SaveChangesAsync();
            }

            return(RedirectToPage("./Index"));
        }
        public async Task <IActionResult> OnPostAsync(int?id)
        {
            if (!ModelState.IsValid)
            {
                return(Page());
            }

            if (id == null)
            {
                return(RedirectToPage("./Index"));
            }


            if (InvoiceModel == null)
            {
                return(NotFound());
            }
            InvoiceModel.ID = (int)id;
            _context.InvoiceTable.Update(InvoiceModel);
            await _context.SaveChangesAsync();

            return(RedirectToPage("./Index"));
        }