public IActionResult OnGet(int?id) { Symptoms = symptomService.GetSymptoms(); if (id.HasValue) { Virus = virusService.GetVirusById(id.Value); if (Virus == null) { return(RedirectToPage("./List")); } foreach (var item in Symptoms) { foreach (var sv in Virus.VirusSymptoms) { if (item.Id == sv.SymptomId) { item.IsSelected = true; } } } } else { Virus = new Virus(); } return(Page()); }