How can I send a list in BeginForm()? - asp.net

Question

Can someone please help me with this problem? At the bottom of my view just before the page loads I create an array of checkboxes like this:
foreach (var course in courses.Select((x, i) => new { Data = x, Index = i }))
{
int currentIndex = course.Index;
String selectedday = "";
String selectedteacher = "";
if (cnt++ % 4 == 0)
{
#: </tr> <tr>
}
#: <td >
<br /><br /><br />
<input type="checkbox" id="checkbox"
name="selectedCourses"
value="#course.Data.CourseID"
#(Html.Raw(course.Data.Assigned ? "checked=\"checked\"" : ""))
/>
I use the same loop to add the assigned state to a list like this:
bool theNewString=course.Data.Assigned ;
String a=theNewString.ToString();
assignedCourses.Add(a);
I defined a list variable at the top of the page so that it can be accessed by the form-wide like this:
#{List<String> assignedCourses =new List<String>(); }
Now I want to send that variable to the controller and this is where things get muddy. If I send a string like this it works fine:
Razor markup
String postedData = "literalString";
#using (Html.BeginForm("Action", "Controller", new { assigned = # postedData }))
Action
[HttpPost]
public ActionResult Edit(int id,List<String> assigned){}
Now if I try this:
#{List<String> assignedCourses =new List<String>(); }
#using (Html.BeginForm("Action", "Controller", new { assigned = #assignedCourses }))
And nothing comes through to the controller. It’s like the list is emptied just before posting. How can send my list to the controller?

Answer 1

I think the way you are trying to create the query string/postback url for the form using the list is wrong and will not produce a properly formatted string.
Maybe try something like this:
#{
List<string> ExampleList = new List<string>();
ExampleList.Add("True");
ExampleList.Add("False");
string param = string.Join("&", ExampleList.ToArray());
}
#using (Html.BeginForm("index", "home", new { #someparam = (new HtmlString(param)) })) { }
This would require you to split the single string up into an array when the action method receives it.
alternatively you can try using RouteValueDictionary instead of list, but this does not support duplicate keys.
Also for checkbox creation try using #Html.CheckBox() as this will automatically create a second hidden input set to false. HTML Forms don't post back checkbox values when they are unchecked, so the second hidden input with the same name will be posted back and you will know it has been unchecked or not checked. MVC will interpret values of "True, False" for the same form key/input name as True and False when just the hidden input with the "False" value is posted back.