Asp.Net Form submit using URL parameters - asp.net-mvc

Question

That's my URL:
http://localhost:7071/TODO?page=1&codcat=56
It returns me a simple form , it is my form of research:
<div class="col-md-8">
#using (Html.BeginForm("Index", "TODO", FormMethod.Get))
{
<p>
Find in ...: #Html.TextBox("SearchString", ViewBag.CurrentFilter as string)
<input type="submit" value="Search" />
</p>
}
<br />
</div>
The Search method in TODO control is :
public async Task<ActionResult> Index(string sortOrder, string currentFilter, string searchString, int? page, int? codcat)
{
ViewBag.CurrentSort = sortOrder;
ViewBag.NameSortParm = String.IsNullOrEmpty(sortOrder) ? "title_desc" : "";
ViewBag.DateSortParm = sortOrder == "Date" ? "date_desc" : "Date";
if (searchString != null)
{
page = 1;
}
else
{
searchString = currentFilter;
}
ViewBag.CurrentFilter = searchString;
var todos = from v in db.TODOs
join cv in db.TODO_CATEGORIA on v.ID equals cv.ID_TODO
where cv.ID_CATEGORIA == codcat select v;
if (!String.IsNullOrEmpty(searchString))
{
todos = todos.Where(s => s.TODO_TITLE.Contains(searchString)
|| s.DESCRIPTION.Contains(searchString)
);
}
switch (sortOrder)
{
case "title_desc":
todos = todos.OrderByDescending(s => s.TODO_TITLE);
break;
case "Date":
todos = todos.OrderBy(s => s.DATE);
break;
case "date_desc":
todos = todos.OrderByDescending(s => s.DATE);
break;
default:
todos = todos.OrderBy(s => s.TODO_TITLE);
break;
}
int pageSize = 21;
int pageNumber = (page ?? 1);
return View(todos.ToPagedList(pageNumber, pageSize));
}
The problem is that the codcat parameter is sent by the form as null.
How could I do to the form keeping the value of the parameter codcat and send the parameter research.

Answer 1

The one way is to use hidden fields.
<input type="hidden" name="codcat" value="#Request.QueryString["codcat"]" />
When submitting a form the POST request is sent to the server, and all your GET request's parameters are left behind.
OR to use this:
public static MvcForm BeginForm(this HtmlHelper htmlHelper, string actionName, string controllerName, object routeValues, FormMethod method);
OR this overload of BeginForm:
public static MvcForm BeginForm(this HtmlHelper htmlHelper, string actionName, string controllerName, FormMethod method, object htmlAttributes);