querystring in URL is allowed or not? - asp.net-mvc-3

Question

my view have two dropdown and one submit buttom if no value is selected and if form get sumbited with GET method then my URL will be http://localhost:53372/question/index?Index=List&type=&stage=&mid=1&mod=5.
but i m applying an ActionFilter with OnActionExcuting() overriden method. so after submitting form URL is like http://localhost:53372/question/index?index=List&mid=1&mod=5.
where other two QueryString is gone?
public override void OnActionExecuting(ActionExecutingContext filterContext)
{
if (filterContext.RequestContext.HttpContext.Request.QueryString["mid"] == null || filterContext.RequestContext.HttpContext.Request.QueryString["mod"] == null)
{
mid = Convert.ToString(HttpUtility.ParseQueryString(filterContext.RequestContext.HttpContext.Request.UrlReferrer.Query)["mid"]);
mod = Convert.ToString(HttpUtility.ParseQueryString(filterContext.RequestContext.HttpContext.Request.UrlReferrer.Query)["mod"]);
if (!string.IsNullOrEmpty(mid) || !string.IsNullOrEmpty(mod))
{
RouteValueDictionary redirecttargetDictionary = new RouteValueDictionary();
NameValueCollection Qstr = null;
if (filterContext.HttpContext.Request.RequestType == "GET")
{
Qstr = HttpUtility.ParseQueryString(filterContext.HttpContext.Request.Url.Query);
foreach (string item in Qstr)
{
redirecttargetDictionary.Add(item, Qstr[item]);
}
if (Qstr["mid"] == null)
{
redirecttargetDictionary.Add("mid", mid);
}
if (Qstr["mod"] == null)
{
redirecttargetDictionary.Add("mod", mod);
}
filterContext.Result = new RedirectToRouteResult(redirecttargetDictionary);
}
}
}
}
but if i select Dropdown value then all queryString is in URL.
QueryString with no values stage=&type= are not allowed?

Answer 1

By default MVC passes data as a query string unless you are submitting a form in which case the query string is bundled as part of the HttpRequest object. You can access the query string directly using the FormCollection object or as part of the HttpRequest object. The most direct way to access the query string is through the FormCollection object as follows
[HttpPost]
public ActionResult SubmitData(FormCollection form)
{
foreach(var key in form.AllKeys)
{
switch(key)
{
case "stage":
// do some work
break;
case "type":
// do some more work
break;
}
}
return RedirectToAction("SomeAction");
}
I have seen empty query string values cause issues with some browsers (I think IE) under certain circumstances. I suggest populating your DropDownList with a token instead of no value such as "Select..." and -1 for the value.
var dropDownList = new List<SelectListItem>();
dropDownList.Add(new SelectListItem{ Text = "Select", Value = "-1"} );
and then
#Html.DropDownList("stage", Model.Stages)
or something like that.
I hope this helps :)