Flash messages lost when set in one action and then displayed after visiting another

[rogersillito]

I'm struggling to get FlashMessages working in the way I want: I am expecting that if I set messages in one action, when I visit (either directly or via a redirect) another action they should be displayed (given appropriate view code). I have put together a test project to show this:

https://gist.github.com/rogersillito/e1b84bd325611c04200e

Essentially, the only way I can get a flash message to display is by setting it in an action that returns a view, and then using the HtmlHelperExtensions method to display the messages within that view. Any attempt to set them in actions that redirect to such a view appear to cause the session contents to be lost?

[bernos]

Im wondering if the issue here is actually down to how the cookie based sessions work in scenarios where Response.AsRedirect is used. If you check out the implementation at https://github.com/NancyFx/Nancy/blob/master/src/Nancy/Session/CookieBasedSessions.cs the current session session is serialised to the cookie at the end of the AfterRequest pipeline. It may be possible that calling Response.AsRedirect is causing the request pipeline to finish before hitting the session serialization code? That would explain why session data set in the request prior to the redirected request is present after redirection, but not session state that was set during the redirected request.

[rogersillito]

I tried to work around what I thought was the issue by saving my own data structure into the nancy session and then using that to set the flash message in the action that returned the view. I just ran into the exact same problem - so your theory stands up based on what I've seen. It may be by design on Nancy's part, but it would render sessions fairly useless in my scenario unfortunately.