title: Persisting QueryString parameters when validation error occurs
body: <p>I have an Upload File form, the file has (Name nvarchar, FileData varbinary(max))</p>
  
  <p>Name and FileData are mandatory fields</p>
  
  <p>For some reason, validation of FileData (using Required attribute) is not working, so I searched the internet and found an Html Helper extension method which renders a Input(file) and can validate it.</p>
  
  <p>But the problem is that when I add the error to the model state and <code>return View()</code> the returnUrl which was in the query string is gone, how can I persist returnUrl and/or some other query string variables in such case?</p>
  
  <p>You may notice, I can't use <code>RedirectToAction</code>, I have to <code>return View()</code> so that the validation summary can show the error (and hopefully, the Name field persists its value).</p>