How to call method in controller from view via ajax?

Question

I create a survey. For whole survey I have only View and for every question partial view. Also I have a pagination. All these demonstrated in the picture below.
Now people can post the form (whole question) to server using GetAnswersMulti method. (I need the form be posted asynchronously). I want to add a feature - when person see the last not answered question - button changes from Answer to Answer and exit. I suppose to do it by removing one button and add another with specific Url. The problem is - server should check if this question is last. I try to call corresponding method in controller asynchronously and get the returned value. I tried much from SO and there is what I came to:
View

<script>
    function isLast(data) {
        $.ajax({
            type: "POST",
            url: "@Url.Action("Survey", "IsLastQuestion")",
            data: { idQuestion: data },
            contentType: "application/json; charset=utf-8",
            dataType: "json",
            success: function (msg) {
                alert("success");
                if (msg == "True") {
                    $(".submitbutton").remove();
                }
            },
            error: function (e) {
                alert("Fail");
            }
        });
    }
</script>

@using (Html.BeginForm("GetAnswersMulti", "Survey", FormMethod.Post))
{
    <input value="Ответить" type="submit"
           class="btn btn-default submitbutton"
           onclick="isLast(@Model.FirstOrDefault().IdQuestion);" />
}

Controller

[HttpPost]
public ActionResult IsLastQuestion(int idQuestion)
{
    Question question = Manager.GetQuestion(idQuestion);
    List<Question> questions = Manager.SelectQuestions(question.idAnketa);
    if (questions.Count == Manager.GetCountQuestionsAnswered(question.idAnketa, SessionUser.PersonID))
        return new JsonResult() { Data = true };
    else
        return new JsonResult() { Data = false };
}
[HttpPost]
public void GetAnswersMulti(List<PossibleAnswerVM> possibleAnswers)
{
    List<Answer> answers = new List<Answer>();
    foreach (PossibleAnswerVM possibleAnswer in possibleAnswers)
    {
        Answer answer = new Answer();
        answer.datetimeAnswer = DateTime.Now;
        answer.idOption = possibleAnswer.IdOption;
        answer.idPerson = SessionUser.PersonID;
        if (possibleAnswer.IsChecked)
        {
            if (IsValid(answer))
                answers.Add(answer);
        }
    }
        Manager.SaveAnswers(answers,possibleAnswers.FirstOrDefault().IdQuestion, SessionUser.PersonID);
}

Now method in controller is called and idQuestion is passed. Method in controller returns true (when it IS the last question). Then I get fail in js code. Help me with this please. I searched 2 days through SO but didn't find anything that works for me.

Answer 1

Maybe better to use Html.Beginform() and use this script:

       <script>
            function isLast(data) {

                $.ajax({
                    type: "POST",
                    url: "@Url.Action("Survey", "IsLastQuestion")",
                    data: { idQuestion : data},
                    contentType: "application/json; charset=utf-8",
                    dataType: "json",
                    success: function (msg){
                        alert($.parseJSON(msg.d));
                        if (msg == "True") {
                           $(".submitbutton").remove();
                }
                    },
                    error: function (e) {
                        alert("Fail");
                    }
                });

            }
        </script>

@using (Html.BeginForm("GetAnswersMulti", "Survey", FormMethod.Post)
<input type="text" id="commentText" placeholder="Введите коментарий"/>
        <input value="Ответить" type="submit"
               class="btn btn-default submitbutton"
               onclick="isLast(@Model.FirstOrDefault().IdQuestion);" />
    }

Answer 2

In order for your action to return Json, then the return type of the action needs to be Json. Since the action returns a boolean value (true or false), then it is not considered as an action method. It needs to return an ActionResult type like so

public ActionResult IsLastQuestion(int idQuestion)
 {
Question question = Manager.GetQuestion(idQuestion);
List<Question> questions = Manager.SelectQuestions(question.idSurvey);
if (questions.Count == Manager.GetCountQuestionsAnswered(
    question.idSurvey,SessionUser.PersonID))
    return Json(new{ d = true});
else
    return Json(new{ d = false});
}

Notice that when I return Json like so return Json(new{ d = true});, there is an anonymous variable d which is the boolean value you will check in your success function like this

success: function (msg){
                    alert($.parseJSON(msg.d));
                    if (msg.d === true) {
                       $(".submitbutton").remove();
            }
                    else if(msg.d == false){
      // Do something if false retured.
     }
    }

Answer 3

Can you try like this?

[HttpGet]
public ActionResult IsLastQuestion(int idQuestion)
{
    Question question = Manager.GetQuestion(idQuestion);
    List<Question> questions = Manager.SelectQuestions(question.idSurvey);
    if (questions.Count == Manager.GetCountQuestionsAnswered(question.idSurvey, SessionUser.PersonID))
        return Content("True", "application/json" );
    else
        return Content("False", "application/json" );
}

In your ajax call-

    function isLast(data) {
    $.ajax({
        type: "GET",
        url: "@Url.Action("Survey", "IsLastQuestion")",
        data: { idQuestion: data },
        contentType: "application/json; charset=utf-8",
        dataType: "json",
        success: function (result)
        {
            //check the value inside result here..
        },
        error: function (e) {
            alert("Fail");
        }
    });
}

Answer 4

Parameter is needed in IsLastQuestion function and you dont pass it in script.

function isLast(parameter) {
    $.ajax({
        type: "POST",
        url: "@Url.Action("Survey", "IsLastQuestion")",
        data: "{parameter}",
        contentType: "application/json; charset=utf-8",
        dataType: "json",
        success: function (msg){
            alert($.parseJSON(msg.d));
        },
        error: function (e) {
            alert("Fail");
        }
    });
    if (isLast2 == true) {
        $(".submitbutton").remove();
    }
}