Question

Can somebody please explain the purpose of TempData in MVC.
I understand it behaves like ViewBag but what does it do beyond that.

Answer 1

TempData is meant to be a very short-lived instance, and you should
only use it during the current and the subsequent requests only! Since
TempData works this way, you need to know for sure what the next
request will be, and redirecting to another view is the only time you
can guarantee this. Therefore, the only scenario where using TempData
will reliably work is when you are redirecting. This is because a
redirect kills the current request (and sends HTTP status code 302
Object Moved to the client), then creates a new request on the server
to serve the redirected view. Looking back at the previous
HomeController code sample means that the TempData object could yield
results differently than expected because the next request origin
can’t be guaranteed. For example, the next request can originate from
a completely different machine and browser instance.

http://rachelappel.com/when-to-use-viewbag-viewdata-or-tempdata-in-asp.net-mvc-3-applications