ASP.NET MVC Int Array parameter with empty array defaults to {0}

Question

I have a controller action like:

Public ActionResult MyAction(int[] stuff){}

I make a JSON request like:

$.getJSON(url, { stuff: [] })

When it gets to C# it looks like an array with one element in it, which is zero (i.e. like if I did int[] stuff = {0};).

Is this new with MVC 2 or .NET 4? It seems to have changed recently, but I haven't found a smoking gun. How can I get around this? This can't possibly be expected behavior, can it?

You'll notice also that this behavior has nothing to do with AJAX/JSON. You'll get the same result if you call your controller and pass "stuff" via the querystring (e.g. /MyAction?stuff= ) — Hector Correa
– Hector Correa, Commented Oct 27, 2010 at 19:10
Very nicely broken down in the accepted answer here: stackoverflow.com/questions/23108272/… — Yashash Gaurav
– Yashash Gaurav, Commented Jun 30, 2020 at 13:40

Xodarap · Accepted Answer · 2010-10-27 21:00:34Z

3

I think this is a bug in MVC:

// create a vpr with raw value and attempted value of empty string
ValueProviderResult r = new ValueProviderResult("", "", System.Globalization.CultureInfo.CurrentCulture);
// this next line returns {0}
r.ConvertTo(typeof(int[]));

If we look at ValueProviderResult.cs in function UnwrapPossibleArrayType, we see:

// case 2: destination type is array but source is single element, so wrap element in array + convert
object element = ConvertSimpleType(culture, value, destinationElementType);
IList converted = Array.CreateInstance(destinationElementType, 1);
converted[0] = element;
return converted;

It forces converted[0] to be element, and ConvertSimpleType casts "" to 0. So I'm closing this question, unless someone has more info.

EDIT: Also, this is not in revision 17270, so if you're making a list of things which change from MVC 1 to MVC 2, this is one of them.

edited Oct 27, 2010 at 21:00

answered Oct 27, 2010 at 20:50

Xodarap

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Comments

Darin Dimitrov · Accepted Answer · 2010-10-28 06:27:39Z

0

When I tested the code I got null array in the controller action and not an array with one element.

In jquery 1.4 and later the way parameters are serialized during an AJAX request have changed and is no longer compatible with the default model binder. You could set the traditional parameter when performing the request:

$.getJSON(url, $.param({ stuff: [ 1, 2, 3 ] }, true));

or

$.ajax({
    url: url,
    type: 'GET',
    dataType: 'JSON',
    data: { stuff: [ 1, 2, 3 ] },
    traditional: true,
    success: function(res) { }
});

answered Oct 28, 2010 at 6:27

Darin Dimitrov

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1 Comment

Xodarap Over a year ago

I'm using traditional, and I still get this. See Hector's comment; the problem still occurs when you just put in the url ?var=

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