Can't pass viewmodel to new action by RedirectToAction

Question

I have a form, when user submit the form, I want to direct the user the new view to display the submitted result(transfer viewmode data to display view).

public class HomeController : Controller
    {
        private MyViewModel _vm;
        .....

        // POST: /Home/Create        
        [AcceptVerbs(HttpVerbs.Post)]
        public ActionResult Create(MyViewModel vm){
           //.....
           //set up vm to temp data _vm
           _vm = vm;

           return RedirectToAction("DisplayData");
        }
        // GET: /Home/DisplayData
        public ActionResult DisplayData()
        {
           //get temp data for display
           return View(_vm);
        }
}

When I posted the form, I can create vm and put it to temp data place _vm. But this _vm can be sent to another action DisplayData, it's null in action DisplayData(). It seems that when redirect action even in same controller, _vm is lost although it is Controller var, not action method var.

How to resolve this problem?

Answer 1

It creates a new instance of the controller as it is a new request therefore as you have found it will be null. You could use TempData to store the vm, TempData persists the data for 1 request only

Good explanation here

Answer 2

One good way is to call

return DisplayData(_vm)

instead of

RedirectToAction("DisplayData")

DisplayData should accept a model anyway.