How to avoid System.ArgumentOutOfRangeException: Index and length must refer to a location within the string. Parameter name: length – Jquery ajax

I’m trying to rewrite some data in DB using Ajax, after passing it to controller I always have the same error: System.ArgumentOutOfRangeException: Index and length must refer to a location within the string. Parameter name: length.

my Ajax code:

tab.on("click", ".edit", function (e) {





    var tr = $(this).closest("tr");
    var id = tr.data("id");
    var fse = $(this).closest("tr").find(".FSE").text();

    var field = $(this).closest("tr").find(".ui-widget");
    var mon = field.find(".desc_NumM");

    var monC = mon.css("background-color");
    var tue = field.find(".desc_NumT");
    var tueC = tue.css("background-color");
    var wed = field.find(".desc_NumW");
    var wedC = wed.css("background-color");
    var thur = field.find(".desc_NumTr");
    var thurC = thur.css("background-color");
    var fri = field.find(".desc_NumF");
    var friC = fri.css("background-color");
    var sat = field.find(".desc_NumSa");
    var satC = sat.css("background-color");
    var sun = field.find(".desc_NumSu");
    var sunC = sun.css("background-color");

    var monVal = mon.text();
    var tueVal = tue.text();
    var wedVal = wed.text();
    var thurVal = thur.text();
    var friVal = fri.text();
    var satrVal = sat.text();
    var sunVal = sun.text();






            $.ajax({
                type: "POST",
                url: "/Home/UpdateWeek",
                data: {
                    id: id,
                    FSE:fse,
                    Monday: monVal,
                    Tuesday: tueVal,
                    Wednesday: wedVal,
                    Thursday: thurVal,
                    Friday: friVal,
                    Saturday: satrVal,
                    Sunday: sunVal,
                    MonColor: monC,
                    TueColor: tueC,
                    WedColor: wedC,
                    ThurColor: thurC,
                    FriColor: friC,
                    SatColor: satC,
                    SunColor: sunC

                },
                dataType: "JSON",
                success: function (data) {

                    alert("Week for: " + fse + " changed!");
                    $('#weekEvents').load(loadWeekData());
                },
                error: function () {
                    alert("Failed, try again");
                }
            });
    });

And here is my controller:

    [HttpPost]
    public JsonResult UpdateWeek(int id, EventsWeek w)
    {

        using (WeekEventsDBEntities db = new WeekEventsDBEntities())
        {
            EventsWeek ewupt = db.EventsWeeks.Where(x => x.Id == id).FirstOrDefault();
            ewupt.Monday = w.Monday.Substring(0, 100);
            ewupt.Tuesday = w.Tuesday.Substring(0, 100);
            ewupt.Wednesday = w.Wednesday.Substring(0, 100);
            ewupt.Thursday = w.Thursday.Substring(0, 100);
            ewupt.Friday = w.Friday.Substring(0, 100);
            ewupt.Saturday = w.Saturday.Substring(0, 100);
            ewupt.Sunday = w.Sunday.Substring(0, 100);
            ewupt.MonColor = w.MonColor.Substring(0, 50);
            ewupt.TueColor = w.TueColor.Substring(0, 10);
            ewupt.WedColor = w.WedColor.Substring(0, 10);
            ewupt.ThurColor = w.ThurColor.Substring(0, 10);
            ewupt.FriColor = w.FriColor.Substring(0, 10);
            ewupt.SatColor = w.SatColor.Substring(0, 10);
            ewupt.SunColor = w.SunColor.Substring(0, 10);
            ewupt.FSE = w.FSE.Substring(0, 20);
            db.SaveChanges();

        }
        return Json(true, JsonRequestBehavior.AllowGet);

    }

debbuger always tell that there is a problem with “Substring(0, 50);”. But the funny thing is, if I change “ewupt.MonColor = w.MonColor.Substring(0, 50);” to “ewupt.MonColor = w.MonColor.Substring(0, 10);” it will work ,but not like it should be. Anyway it will be no more error ans data will be passed to my DB… What I’m doing wrong here?