MVC4: request[field] returning System.Web.Mvc.SelectListItem unexpectedly - asp.net-mvc-4

Question

I have an Index page which shows a list of data. The list can be filtered by selection from a dropdown list. This works okay. The first item in the dropdown has a blank value and the text "(all users)." So, this does what you expect--it shows all values in the list if you don't select an item to filter by. The razor for this is pretty simple:
#using (Html.BeginForm())
{
#Html.Label("userName", "View user:")
#Html.DropDownList("userName", ViewBag.UserName as SelectList, new { onchange = "this.form.submit()" })
}
In addition to viewing the list of data on the page, I offer a text file download of the currently filtered items. The razor for this is also pretty simple:
#using (Html.BeginForm("Download", "Checkout"))
{
#Html.Hidden("userName", Request["userName"])
<input type="submit" value="Download Metadata from Checked Out Files" />
}
This works right IF there's something selected in the filter dropdown. But if nothing is selected, then Request["userName"] returns "System.Web.Mvc.SelectListItem". I want it simply to be blank as the dropdown list appears when nothing is selected. What happens is that the value System.Web.Mvc.SelectListItem is passed to my download action and treated as a filter value.
So, the question is how to make it so a blank selection in my filter dropdown is not mistaken for "System.Web.Mvc.SelectListItem."

Answer 1

Try changing your #Html.DropDownList to this overload, string.Empty gives you the default blank option in your dropdown
#Html.DropDownList("userName", ViewBag.UserName as SelectList, string.Empty, new { onchange = "this.form.submit()" })
I hope I didn't misunderstand your question!