Preventing users from skipping pages in an ASP.NET form - asp.net

Question

I have a data entry form that I've broken apart into 5 pages and I want to make sure that the users go through the pages in the proper order each time. The navigation is set up to take them through it properly, including a breadcrumb to go back and change previous pages. I want to make sure, however, that they don't get to a later page without going through the earlier pages first (i.e., go through pages A and B then skip to D by entering the URL directly, or start out on D using a bookmark).
I've made some attempts to prevent this, with my latest one being this, which checks for required session variables specific to each page:
public static string CheckForPageSkipping()
{
var redirectTo = "";
if (HttpContext.Current.Session["TestDate"] == null) redirectTo = "~/Auth/SignOff.aspx";
if (HttpContext.Current.Session["Repairs"] == null) redirectTo = "~/Auth/RepairNotes.aspx";
if (HttpContext.Current.Session["MeterNum"] == null) redirectTo = "~/Auth/TestResults.aspx";
if (HttpContext.Current.Session["PremiseOwner"] == null) redirectTo = "~/Auth/PremiseInfo.aspx";
return redirectTo;
}
I called this during each Page_Load event and redirected to the page it returned if it was not the page they were on. This almost worked, until I realized that it prevents you from being able to navigate backwards (it always sends you back to the latest page you haven't completed). I'm sure I can cobble something together to make this work, but I wanted to see if there is a better way to do it. Something either built in to ASP.NET, or something more elegant that someone had built in the past.
My search attempts, both in Google and on StackOverflow, yielded no useful results. Maybe I was using the wrong terms, but it was mostly stuff like I've written here (the suggestions made at the top now have not been helpful either).

Answer 1

It seems like you have control of the pages so why not get rid of them and put the code into user controls, register these controls in one page in panels or placeholders and control the visibility of these panels in the code so that you can properly enforce the order in which these are visited?

Answer 2

Have you looked at the <asp:wizard> built-in control? I think it will fit your needs and you can configure it for many different scenarios.
Here is a link describing its use: http://msdn.microsoft.com/en-us/magazine/cc163894.aspx
Also see the current official documentation: MSDN Library

Answer 3

There is a good pattern explained here for using multi-part forms using panels.
Multi-Part Form using Panels

Answer 4

If you don't want to use the Wizard control and you don't want to use Panels, either Server.Transfer or Cross Page Posting should work. With either method, checking the PreviousPage should cover your page skipping concerns.
Server.Transfer has the URL oddity you mentioned, but is otherwise pretty straightforward.
Cross-Page Posting is quite appropriately tailored to your needs as well.
Post each form to the next form page.
Receive and process the data there (with strong typing if you set it
up correctly).
Only load the new page if everything checks out (PreviousPage is
correct, data is valid).
I admit, I don't have direct experience using either of these methods myself, but I can see how they could be implemented to handle your situation.