What's the best way to deal with cache and the browser back button?

Question

What's the best way to handle a user going back to a page that had cached items in an asp.net app? Is there a good way to capture the back button (event?) and handle the cache that way?

Answer 1

You can try using the HttpResponse.Cache property if that would help:

Response.Cache.SetExpires(DateTime.Now.AddSeconds(60));
Response.Cache.SetCacheability(HttpCacheability.Public);
Response.Cache.SetValidUntilExpires(false);
Response.Cache.VaryByParams["Category"] = true;

if (Response.Cache.VaryByParams["Category"])
{
   //...
}

Or could could block caching of the page altogether with HttpResponse.CacheControl, but its been deprecated in favor of the Cache property above:

Response.CacheControl = "No-Cache";

Edit: OR you could really go nuts and do it all by hand:

Response.ClearHeaders();
Response.AppendHeader("Cache-Control", "no-cache"); //HTTP 1.1
Response.AppendHeader("Cache-Control", "private"); // HTTP 1.1
Response.AppendHeader("Cache-Control", "no-store"); // HTTP 1.1
Response.AppendHeader("Cache-Control", "must-revalidate"); // HTTP 1.1
Response.AppendHeader("Cache-Control", "max-stale=0"); // HTTP 1.1 
Response.AppendHeader("Cache-Control", "post-check=0"); // HTTP 1.1 
Response.AppendHeader("Cache-Control", "pre-check=0"); // HTTP 1.1 
Response.AppendHeader("Pragma", "no-cache"); // HTTP 1.1 
Response.AppendHeader("Keep-Alive", "timeout=3, max=993"); // HTTP 1.1 
Response.AppendHeader("Expires", "Mon, 26 Jul 1997 05:00:00 GMT"); // HTTP 1.1 

Answer 2

As far as I know (or at least have read) is its best to try not to work in response to user events, but rather think "in the page"..

Architect your application so it doesn't care if the back button is pushed.. It will just deal with it.. This may mean a little extra work from a development point of view, but overall will make the application a lot more robust..

I.e if step 3 performs some data chages, then the user clicks back (to step 2) and clicks next again, then the application checks to see if the changes have been made.. Or ideally, it doesnt make any hard changes until the user clicks "OK" at the end.. This way, all the changes are stored and you can repopulate the form based on previously entered values on load, each and every time..

I hope that makes sense :)