TempData Not Being Cleared

Below are some of the key points to note when using Temp data.

1) A read access to temp data doesn't remove items from the dictionary immediately, but only marks for deletion.

2) Temp data will not always remove the item that has been accessed. It only removes the item when an action results in an Http 200 status code (ViewResult/JsonResult/ContentResult etc).

3) In case of actions that result in an Http 302 (such as any redirect actions), the data is retained in storage even when it is accessed.

Fixed by adding TempData.Remove right after i read it.

Not really happy about this. I thought the whole point of TempData was that i didn't have to do this.

May as well be using Session directly.

There are 2 GET HTTP requests involved here:

1. The first request is sent by the client and is the one which stores something into TempData
2. At the end of the first request the client sends a second HTTP request to fetch the logon page.

There is no POST request involved in your scenario. The fact that from your GET Foo action you are invoking the POST Foo action doesn't mean that there is a separate request being performed (you are still in the context of the initial GET request). It is only a C# method call, not a separate request.

You store something into TempData during the first request and this TempData will be available for the second one. So it will be available in the controller action rendering the logon page.

So you must read from TempData in action rendering the logon page if you want TempData to be removed.