Question

I have a form in my asp.net mvc view as follow:

 <%using (Html.BeginForm("SearchBorrowed", "Admin", FormMethod.Get))
          { %>
        <%: Html.TextBox("searchTerm", Request.QueryString["searchterm"])%>
        <input type="submit" value="Search" />
        <br />
        Is Returned :
        <%:Html.CheckBox("IsReturned")%>
        <%} %>

and here is the ‘SearchBorrowed’ action:

public ActionResult SearchBorrowed(bool IsReturned=false, string searchTerm = null)
        {
            IEnumerable<BorrwoinfInfo> bs;

            //...Get from repository

            return View(bs.ToList());

        }

and finally routing settings :

  routes.MapRoute(
            "SearchBorrowed", // Route name
            "{controller}/{action}/{*searchTerm}", // URL with parameters
            new
            {
                controller = "Admin",
                action = "SearchBorrowed",

                searchTerm = UrlParameter.Optional
            } // Parameter defaults

when I submit the form without checking ‘IsReturned’ Checkbox,
it returns result and the url gets as follow :

…/SearchBorrowed?searchterm=&IsReturned=false

But when I check IsReturned’ Checkbox, the urls gets like this:

…/SearchBorrowed?searchterm=s&IsReturned=true&IsReturned=false

Why there is two IsReturned in above url ?!

How Could I fix this ?

Answer 1

Why there is two IsReturned in above url ?!

Because the Html.CheckBox helper generates an additional hidden input field with the same name as the checkbox. If you look at the generated HTML you will see that the helper generated the following 2 input fields:

<input type="checkbox" name="IsReturned" id="IsReturned" value="true" checked="checked" />
<input type="hidden" name="IsReturned" id="IsReturned" value="false" />

This is by design. This helper is intended to be bound to a boolean property on your view model. When a checkbox field is not checked no value is sent to the server, so if there was not no hidden field you wouldn’t be able to bind it to a boolean field.

If you don’t want this hidden field you could either write a custom helper or generate the checkbox field manually.