AJAX not passing Handsontable Data to Controller

Question

I am attempting to pass data between my view and controller using AJAX and jQuery.

//Creates Container for Default Table
var container = document.getElementById('example');
var userInput = new Handsontable(container, {
    minCols: 10,
    minRows: 5,
    minSpareRows: 1,
    rowHeaders: true,
    colHeaders: [//Column Headers],
    contextMenu: true
});

//Load the Button with the AJAX Command
$(document).ready(function () {
    $("#send").click(function () {

        $.ajax({
            url: '@Url.Action("ProcessRequest","ControllerName")',
            data: JSON.stringify({
                Label1: userInput.getDataAtCol(1),
                Label2: userInput.getDataAtCol(2),
                Label3: userInput.getDataAtCol(3),

            }),
            dataType: 'json',
            contentType: "application/json; charset=utf-8",
            type: 'POST',
            success: function (result) {
                alert("Succes");
            },
            error: function (result) {
                alert("Failure");
            }
        });
    });
});

, However, when I check my server side code (in C#) it is saying that the value of my label variables is null.

[HttpPost]
    public JsonResult ProcessRequest(
        string Label1,
        string Label2,
        string Label3)
   {
        var _Label1 = Label1;
        var _Label2 = Label2;
        var _Label3 = Label3;

        string message = string.Format("Successful.");
        return Json(new { Success = true, Message = message });
    }

}

Does the error have to do with the with how 'data' in the AJAX command is formatted, or am I having a type error somewhere? Any help would be greatly appreciated!

Answer 1

Turns out that I needed to make a separate variable containing my data and stringify it twice: once as an independent call, and again in the ajax as JSON.stringify'{data: varaibleName}. For some reason,the getDataAtCol() methods were indeed returning data, but the results had to be stringified once before they could be stringified in the AJAX. Thank you @David and @ZekeDroid for the help, it's greatly appreciated!