Empty data send by json - ajax

Question

For unknown reason for me data received by my function in controller is always null.
My data is translated into json properly. Data is send but not received (sending ends with success).
Here You can see my Ajax function
$.ajax({
url: "/Devices/Read",
contentType: "text",
type: "POST",
datatype: "json",
data: ko.toJSON(self),
error: function (xmlHttpRequest, errorText, thrownError) {
console.log("error")
},
success: function (data) {
if (data != null) {
console.log("success");
}
}
});
here my function in controller:
[HttpPost]
public ActionResult Read(string data)
{
return Json(new Object());
}
I tried:
changing parameter type to: Object, String
changing contentType to : text, application/json; charset=utf-8
Still no efects. Can anyone suggest me where should I search for mistake?
UPDATE:
After changing method declaration to:
public ActionResult Read(object[] data, string DeviceUser, string DeviceId, string number)
Last three strings are OK but first object consist of proper number of elements but they are null.
in JS they are alements in array of classes
structure of my JS objects:
var Eq = function (name, price) {
var self = this;
self.DeviceSerialNumber = ko.observable();
self.Batch = ko.observable();
};
var ViewModel = function () {
var self = this;
self.data = ko.observableArray([]);
self.DeviceUser = ko.observable();
self.DeviceId = ko.observable();
self.number = ko.observable(1);
};

Answer 1

In your controller action, why do you:
return RedirectToAction("Index");
I think you may want to:
return Json(data);

Answer 2

If you are writing an HTTP Post method, then the redirect to action does not really make sense, because you are posting data, not requesting a page.
You could do something like this:
[HttpPost]
public ActionResult Read(string Data)
{
return Json(Data);
}

Answer 3

OK problem was in setting proper parameter type in method.
TO solve my problem I need to modify method declaration to:
public ActionResult Read(ViewModel m)
and add ViewModel like this:
public class ViewModel
{
public List<InnerClass> data { get; set; }
public string DeviceUser {get;set;}
public string DeviceId {get;set;}
public int number {get;set;}
}
public class InnerClass
{
public string DeviceSerialNumber { get; set; }
public string Batch { get; set; }
}
now all data is received.
Thanks You all for help and suggestions. I will give you all +1 :)