public async Task <IActionResult> OnPostAsync(int id) { if (ModelState.IsValid && !string.IsNullOrWhiteSpace(Author.LastName)) { try { Author.Id = id; db.Attach(Author).State = EntityState.Modified; await db.SaveChangesAsync(); } catch (DbUpdateConcurrencyException ex) { ViewData["Error"] = $"UpdateConcurrencyException: {ex.Message}"; return(RedirectToPage("./Index")); } } return(RedirectToPage("./Index")); }