Question

I have a controller action in my project that has a situation where it needs to display an error message to the user under certain scenarios. This action occurs in a POST:

[HttpPost]
public ActionResult DoSomeAction() {
    if( someCondition )
        return RedirectToAction("SomeActionError");

    return RedirectToAction("Index");
}

public ActionResult SomeActionError() {
    return View();
}

Currently I have it set up so that it will redirect to an error controller action. I’m not really fond of this approach because in the URL they see /SomeActionError and it also means that the user can directly navigate to this URL.

Is it a bad design/approach to put some flag in TempData and redirect to another controller that checks for the TempData error flag?

Example:

[HttpPost]
public ActionResult DoSomeAction() {
    if( someCondition ) {
        TempData["DoSomeActionError"] = true;            
    }

    return RedirectToAction("Index");
}

public ActionResult Index() {
    // check for error
    if( TempData["DoSomeActionError"] ) {
        return View("SomeActionError");
    }
}

Is this a bad idea? Is there another approach that does something similar (doesn’t allow the user to directly navigate to the error action)? I don’t want to return the View on the POST action because I don’t want them to refresh and cause another POST.

Answer 1

TempData is not per se a bad concept. TempData is for transporting an information to some consumer that reads that information and the information should vanish after it’s been read.

The way your’re using TempData is odd. A more elegant implementation for your requirements (you should show an error message) is to implement an equivalent to the rails flash concept and don’t redirect to an error page but display an error message in your index view. Something like a red banner that says “The record could not be saved”.

This question shows a nice flash implementation including the view stuff (not the accepted answer but the answer by @jim)