Why is passing a JSON array to a controller action not working?

Question

My javascript

function SaveData(status) {
    var reserved = [];
    var id = -1;
    $('#fdEitDetail').find('table tr').each(function (index, item) {
        var isChk = $(item).find('input:checkbox').is(':checked') ? 0 : 1;
        id = $(item).attr('name');
        reserved.push({ ID: $(item).attr('id'), IsChecked: isChk, Comment: $(item).find('textarea').val() });
    });

    var dataset = JSON.stringify({ checkList: reserved, status: status, machineID: id });
    $.ajax({
        url: '/Home/UpdateData',
        contentType: "application/json; charset=utf-8",
        type: 'POST',
        data: dataset,
        success: function (result) {
            alert(result);
        }
    });
}

I am calling this controller action:

public JsonResult UpdateData(string checkList, int status,int machineID)
{
    var response = 
        new JavaScriptSerializer().Deserialize<List<PMICheckListRequest>>(checkList);

    return Json("value = Success");
}

the class

public class PMICheckListRequest
{
    public int ID { get; set; }
    public int IsChecked { get; set; }
    public string Comment { get; set; }
}

In the controller action is being hit from the ajax request both of this parameterstatus, machineID has the value that i set in javascript but checkList is null always.

Darin Dimitrov · Accepted Answer · 2014-01-22 13:42:53Z

3

Just use a view model and stop hanging around those strings that you need to be parsing:

public class MyViewModel
{
    public PMICheckListRequest[] CheckList { get; set; }
    public int Status { get; set; }
    public int MachineID { get; set; }
}

as parameter to your controller action:

public ActionResult UpdateData(MyViewModel)
{
    // NO NEED TO BE DOING ANY PLUMBING DESERIALIZATION HERE
    // THE VIEW MODEL ALREADY CONTAINS EVERYTHING YOU NEED

    return Json("value = Success");
}

Notice how the view model already contains an array of PMICheckListRequest where each element has properties ID, IsChecked and Comment which you already populate in the AJAX request.

answered Jan 22, 2014 at 13:42

Darin Dimitrov

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Comments

rae1 · Accepted Answer · 2014-01-22 13:48:21Z

The reason the checkList parameter is null it is because you are trying to bind a complex object JSON array (i.e [{}, {}]) to a string, when the types aren't really compatible.

Try this instead,

public JsonResult UpdateData(
    List<PMICheckListRequest> checkList, 
    int status, 
    int machineID)
{
    return Json("value = Success");
}

You do not have to deserialize it manually; the model binder will do that for you.

As a extra note, it is not a bad idea to create a view model to hold the data in a more organized way, the way @DarinDimitrov shows,

public JsonResult UpdateData(
    PMICheckListRequestViewModel model)
{
    return Json("value = Success");
}

...

public class PMICheckListRequestViewModel
{
    public List<PMICheckListRequest> CheckList { get; set; }

    public int Status { get; set; }

    public int MachineID { get; set; }
}

It will prove more flexible in the future.

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