Proper technique to pass javascript array to controller with List<int> parameter

Question

I have a controller that takes a List<int> and I am calling from AJAX. The controller is hit, but the parameter is always null.

My controller:

public ActionResult MinorAreas(List<int> majorareas)
{
    // ...
}

jQuery call:

function onChange(e)
{
   var cur = this.value(); // an array of numbers like [2,4,7,9]

   $.ajax({
       cache: false,
       type: "GET",
       traditional: true,
       url: "@(Url.RouteUrl("GetMinorAreas"))",
       data: { "majorareas": cur},
       success: function (data) {...},
       error: function (xhr, ajaxOptions, thrownError) {... }
   });

 }

Route definition:

routes.MapLocalizedRoute(
    "GetMinorAreas",
    "minorAreas",
    new { controller="ProSearch", action="MinorAreas", majorareas=new List<int>() },
    new[] { "ABC.ZZZ.Controllers" }
);

Using fiddler, I can see that the URI is built correctly:

# With an array of [2]
http://localhost:15536/minorAreas?majorareas=2&_=1450307693166

# With an array of [2,3,9]
http://localhost:15536/minorAreas?majorareas=2&majorareas=3&majorareas=9&_=1450308261808

I've already looked at this question about passing arrays to a controller with a List<int> parameter, but the solution doesn't seem to work for me. What am I doing wrong?

Can you edit and provide the actual network request? Your JSON may not be formatted properly. — Nate Barbettini
– Nate Barbettini, Commented Dec 16, 2015 at 21:43
Ohhh duh...I should have thought of that. Yes coming right up. — GPGVM
– GPGVM, Commented Dec 16, 2015 at 21:44
It does look like the values are being passed (as separate querystring arguments), which should work. Does this have to be a GET? You might have more luck with a POST. — Nate Barbettini
– Nate Barbettini, Commented Dec 16, 2015 at 23:29
Why are you doing majorareas=new List<int>() in the route definition? — Nate Barbettini
– Nate Barbettini, Commented Dec 16, 2015 at 23:31

Nate Barbettini · Accepted Answer · 2015-12-17 00:02:56Z

1

It looks like the network request is being generated correctly. The problem is in the route definition:

routes.MapLocalizedRoute(
    "GetMinorAreas",
    "minorAreas",
    new { controller="ProSearch", action="MinorAreas", majorareas=new List<int>() },
    new[] { "ABC.ZZZ.Controllers" }
);

majorareas=new List<int>() is going to ensure that majorareas is always an empty list, even when it otherwise would be populated!

You don't have to define parameters here; the method definition in the controller does that. Leave it off, and it should work fine:

routes.MapLocalizedRoute(
    "GetMinorAreas",
    "minorAreas",
    new { controller="ProSearch", action="MinorAreas" },
    new[] { "ABC.ZZZ.Controllers" }
);

answered Dec 17, 2015 at 0:02

Nate Barbettini

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