Passing TempData from action filter to action

Question

I've been trying to pass TempData from ActionFilter to the action using :

filterContext.Controller.TempData.Add("Key","Value");

However, it appears that no TempData is passed to the action as I keep getting the Object not referenced to an instance of the object error.

Is this the right way to pass TempData to the controller from the ActionFilter ? if not, how can I do this ?

Answer 1

This will work :-

Answer 1 :

Filter :-

public class MyCustomAttribute : ActionFilterAttribute
{
  public override void OnActionExecuting(ActionExecutingContext filterContext)
  {
    filterContext.RouteData.Values.Add("Key","Value");
  }
}

Controller :-

[MyCustom]
public ActionResult Index()
{
    TempData["Key"] = RouteData.Values["Key"];

    return View();
}

Answer 2 :

Filter :-

public class MyCustomAttribute : ActionFilterAttribute
{
    public override void OnActionExecuting(ActionExecutingContext filterContext)
    {
        filterContext.Controller.TempData.Add("Key","Value");
    }
}

Controller :-

[MyCustom]
public ViewResult Index()
{
    string Tempval = TempData["Key"].ToString();
    return View();
}

Answer 2

Filter code:

public class MyWhateverAttribute : ActionFilterAttribute
{
    public override void OnActionExecuting(ActionExecutingContext filterContext)
    {
        filterContext.Controller.TempData.Add("some key", "some value");
    }
}

Action code:

[MyWhatever]
public ViewResult Index()
{
    string value = TempData["some key"] as string;
    return View();
}

Note: you must ensure that your filter code is executed before the action code in order to pass some value, that's why OnActionExecuting is the method that needs to be overridden