ASP.NET MVC how can I return an error from a file download action without leaving the current page?

Question

I am calling a file download action from javascript:

$elem.click(function() { 
    window.location.href = 'MyController/MyFileDownloadAction';
});

The controller returns a file:

[AcceptVerbs(HttpVerbs.Post)]
public ActionResult MyFileDownloadAction()
{
    /* do some processing, generate an in-memory file... */

    return File(myFileStream, "text/plain", myFileName);
}

This action has a pretty high likelyhood of throwing an exception (or at least not being able to return the file).

Due to the nature of the application (which contains a lot of dynamic content), I can't really redirect to an error page in this situation. The current page needs to stay open somehow.

So I'm ideally looking for something like a javascript pop-up, but afaik this isn't going to be possible since I don't know any way to return a javacript instruction in a non-ajaxed controller call. If I display an error page I need to force it to open in a new window some how. Is there any possible solution to this problem?

Answer 1

I don't believe it's possible to do what you want. As soon as you do a "window.location.href = 'somelocation'", you are instructing the current browser window to request 'somelocation' and render the result, whatever it may be. Therefore, you need to output whatever error information in the result to that request.

Now, there is no reason that you would need to redirect to an error page. You could return a ViewResult containing the error message or any other kind of result.