Passing data through RedirectToPage

Question

I have a ASP.NET Core RazorPages visitor management project that I'm working on where I need to pass an instance of a class from one page to another page using the RedirectToPage method.
Process: a visitor first fills out their information on the Create page, the info is posted to the database and then the instance of the visitor is passed to the second page where the data is formatted and screenshotted to post a jpeg to the instance of the visitor in the database.
I've been trying the data pass methods suggested in other posts, but I'm having difficulty translating MVC to RazorPages. I don't think I can use TempData or ViewData given that I need to both post to a database and add to the specific visitor entry in the database, so I've been looking through Microsoft's docs on the RedirectToPage methods, as well as this post on the different methods. I think I need to use the PRG Pattern approach with RedirectToPage(string, string, string) that accepts the parameters pageName, pageHandler, and fragment. The part I'm having trouble with is the second page model's code (RegistrationSuccess.cshtml.cs) in calling the visitor instance.

This is the relevant code from Create.cshtml.cs:

 public class CreateModel : PageModel
{
    private readonly VisitorManagementSystem.Data.VisitorManagementSystemContext _context;
    [BindProperty]
    public Visitor Visitor { get; set; }

    public CreateModel(VisitorManagementSystem.Data.VisitorManagementSystemContext context)
    {
       _context = context;
    }

    public IActionResult OnGet()
    {
        return Page();
    }
        
    public async Task<IActionResult> OnPostAsync()
    {
        if (!ModelState.IsValid)
        {
            return Page();
        }
        //....
        _context.Visitor.Add(Visitor);
        await _context.SaveChangesAsync();
        return RedirectToPage("./RegistrationSuccess", "Visitor", new { visitorId  = Visitor.ID.ToString() });
    }
}

RegistrationSuccess.cshtml.cs

public class RegistrationSuccessModel : PageModel
{
    [BindProperty]
    public Visitor Visitor { get; set; }
    private readonly VisitorManagementSystem.Data.VisitorManagementSystemContext _context;
    public RegistrationSuccessModel(VisitorManagementSystem.Data.VisitorManagementSystemContext context)
    {
        _context = context;
    }
    
    //This is where I'm not sure what the correct syntax is to call the instance of the visitor
    public IActionResult OnGet(string visitorId)
    {
        //from the visitorId value, get the object
        Visitor = VisitorManagementSystem.GetVisitor(visitorId);
        return Page();
    }
    public async Task<IActionResult> OnPostAsync()
    {
        return RedirectToPage("/Visitors/RegistrationSuccess");
    }
}

I've tried using the RedirectToPage(string, object) method, but this has two problems: all of the visitor's info is displayed in the URL, which seems insecure; also, I get the error "This site can't be reached ERR_HTTP2_PROTOCOL_ERROR"
I'm a novice, so I appreciate any help!

Serge · Accepted Answer · 2021-07-22T21:12:03.090

2

You should add to the top of your RegistrationSuccess.cshtml.cs razor page

@page "{visitorId}"

and from the action

  return RedirectToPage("./RegistrationSuccess", new { visitorId  = Visitor.ID.ToString() });

and fix the action

public IActionResult OnGet(string visitorId)
    {
   if (!string.IsNullOrEmpty(visitorId))
Visitor = _context.Set<Visitor>().FirstOrDefault( i=> i.VisitorId==visitorId);
return Page();

    }

edited Jul 22 '21 at 21:12

answered Jul 22 '21 at 20:10

Serge

40,935
4
18
45

When I make these changes, the RegistrationSuccess still can't call the visitor--it throws System.NullReferenceException:'Object reference not set to an instance of an object'. Is there something I need to change/add in the OnGet method in RegistrationSuccess.cshtml.cs? (Visitor = VisitorManagementSystem.GetVisitor(visitorId) isn't recognized) – PacifismPostMortem Jul 22 '21 at 20:53
@PacifismPostMortem The most important is do you get visitorId in get of RegistrationSuccessModel ? And where is declared VisitorManagementSystem ? You use it to GetVisitor(visitorId); – Serge Jul 22 '21 at 21:02
@PacifismPostMortem did you try Visitor = _context.Set().FirstOrDefault( i=> i.VisitorId==visitorId); ? – Serge Jul 22 '21 at 21:23
Sorry about that, didn't see your edit until after I had posted the comment; that solves the problem. Thank you for your help! – PacifismPostMortem Jul 22 '21 at 21:36

Passing data through RedirectToPage

1 Answers1