Question

I’ve disabled sessionState in my mvc2 app via the web.config and also created my own controllerfactory and dummy tempdata provider, as described here:

How can I disable session state in ASP.NET MVC?

Only I’ve made it so that SaveTempData throws an exception:

 public void SaveTempData(ControllerContext controllerContext, 
                          IDictionary<string, object> values)
    {
        throw new NotImplementedException(
        "Cannot set tempdata, no session state is available.");
    }

I’ve made sure that no code is ever using either the Session or the TempData objects, but I still see this exception getting thrown after the “OnResultExecuted” event has been raised. I used to use this very same pattern on my mvc1 site and never saw the exception. Any ideas?

If I change my “SaveTempData” implementation to this:

public void SaveTempData(ControllerContext controllerContext, 
                         IDictionary<string, object> values)
    {
        if (values.Count != 0)
        {
            throw new NotImplementedException(
            "Cannot set tempdata, no session state is available.");
        }
    }

Everything works as expected – I’m just hoping to learn why SaveTempData is called at all when I’m not using it anywhere.

Update

Discovered this article: http://www.gregshackles.com/2010/07/asp-net-mvc-do-you-know-where-your-tempdata-is/

Which explains that ExecuteCore calls PossiblyLoadTempData and PossiblySaveTempData around an action – which is what was causing my issue. Is this a new addition in mvc2 vs. mvc1?

Answer 1

That’s how it is implemented in the Controller.ExecuteCore method. The LoadTempData and SaveTempData methods will always be called before and after each action so make sure that they do not throw an exception. In order to disable the session effectively I would recommend you putting the following in your web.config:

<sessionState mode="Off" />