Question

I’m trying to pass an array of objects into an MVC controller method using
jQuery’s ajax() function. When I get into the PassThing() C# controller method,
the argument “things” is null. I’ve tried this using a type of List for
the argument, but that doesn’t work either. What am I doing wrong?

<script type="text/javascript">
    $(document).ready(function () {
        var things = [
            { id: 1, color: 'yellow' },
            { id: 2, color: 'blue' },
            { id: 3, color: 'red' }
        ];

        $.ajax({
            contentType: 'application/json; charset=utf-8',
            dataType: 'json',
            type: 'POST',
            url: '/Xhr/ThingController/PassThing',
            data: JSON.stringify(things)
        });
    });
</script>

public class ThingController : Controller
{
    public void PassThing(Thing[] things)
    {
        // do stuff with things here...
    }

    public class Thing
    {
        public int id { get; set; }
        public string color { get; set; }
    }
}

Answer 1

Using NickW’s suggestion, I was able to get this working using things = JSON.stringify({ 'things': things }); Here is the complete code.

$(document).ready(function () {
    var things = [
        { id: 1, color: 'yellow' },
        { id: 2, color: 'blue' },
        { id: 3, color: 'red' }
    ];      
    
    things = JSON.stringify({ 'things': things });

    $.ajax({
        contentType: 'application/json; charset=utf-8',
        dataType: 'json',
        type: 'POST',
        url: '/Home/PassThings',
        data: things,
        success: function () {          
            $('#result').html('"PassThings()" successfully called.');
        },
        failure: function (response) {          
            $('#result').html(response);
        }
    }); 
});


public void PassThings(List<Thing> things)
{
    var t = things;
}

public class Thing
{
    public int Id { get; set; }
    public string Color { get; set; }
}

There are two things I learned from this:

1. The contentType and dataType settings are absolutely necessary in the ajax() function. It won’t work if they are missing. I found this out after much trial and error.

2. To pass in an array of objects to an MVC controller method, simply use the JSON.stringify({ ‘things’: things }) format.