سلام من یک جدول Person دارم که اطلاعات شخص رو ذخیره میکنه و دوتا فیلد داره برای اسم شهر و مدرک شخص که کلید خارجی هستند از جدول های City و Madrak :

وقتی میخوام اطلاعات رو ذخیره کنم خطا میده.فکر میکنم مشکل از DropDownList هام باشه چون اون ها رو با ViweModel مقدار دادم :

کدهام به صورت زیر هستند:

کد اکشن ایجاد شخص جدید :

 [HttpGet]
        public ActionResult CreatePerson()
        {
            db.Configuration.ValidateOnSaveEnabled = false;
            var City = db.City.ToList();
            var madrak = db.Madrak.ToList();
            //var model = new VM_AddPerson(City, madrak);

            var model = new VM_AddPerson
            {
                City = City,
                Madrak = madrak
            };
            return View(model);
        }


        [HttpPost]
        public ActionResult CreatePerson(Person per)
        {
            db.Configuration.ValidateOnSaveEnabled = false;
            try
            {
                Person p = new Person();

                p.FirstName = per.FirstName;
                p.LastName = per.LastName;
                p.UserName = per.UserName;
                p.MadrakID = per.MadrakID;
                p.Stutus = false;
                p.PassWord = per.PassWord;
                p.CityID = per.CityID;

                p.Address = per.Address;
                p.Email = per.Email;
                p.Image = per.Image;

                db.Person.Add(p);
                db.SaveChanges();

                return RedirectToAction("ShowPerson", "Home");
            }
            catch
            {
                return View();
            }
           
        }

   }

کد ویو ام به صورت زیر هست :

@model WebApplication1.ViewModels.VM_AddPerson

@{
    ViewBag.Title = "CreatePerson";
    Layout = "~/Views/Shared/_Layout.cshtml";
}

<h2>CreatePerson</h2>

@using (Html.BeginForm("CreatePerson","Home",FormMethod.Post)) 
{
    @Html.AntiForgeryToken()
    
    <div class="form-horizontal">
        <h4>Person</h4>
        <hr />
        @Html.ValidationSummary(true, "", new { @class = "text-danger" })
        <div class="form-group">
            @Html.LabelFor(model => model.Person.FirstName, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.EditorFor(model => model.Person.FirstName, new { htmlAttributes = new { @class = "form-control" } })
                @Html.ValidationMessageFor(model => model.Person.FirstName, "", new { @class = "text-danger" })
            </div>
        </div>

        <div class="form-group">
            @Html.LabelFor(model => model.Person.LastName, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.EditorFor(model => model.Person.LastName, new { htmlAttributes = new { @class = "form-control" } })
                @Html.ValidationMessageFor(model => model.Person.LastName, "", new { @class = "text-danger" })
            </div>
        </div>

        <div class="form-group">
            @Html.LabelFor(model => model.Person.PassWord, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.EditorFor(model => model.Person.PassWord, new { htmlAttributes = new { @class = "form-control" } })
                @Html.ValidationMessageFor(model => model.Person.PassWord, "", new { @class = "text-danger" })
            </div>
        </div>

        <div class="form-group">
            @Html.LabelFor(model => model.Person.UserName, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.EditorFor(model => model.Person.UserName, new { htmlAttributes = new { @class = "form-control" } })
                @Html.ValidationMessageFor(model => model.Person.UserName, "", new { @class = "text-danger" })
            </div>
        </div>

        <div class="form-group">
            @Html.LabelFor(model => model.Person.CityID, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.DropDownListFor(model => model.Person.CityID, new SelectList(Model.City, "CityID", "CityName"),"شهر خود را انتخاب کنید")
                @Html.ValidationMessageFor(model => model.Person.CityID, "", new { @class = "text-danger" })
            </div>
        </div>

        <div class="form-group">
            @Html.LabelFor(model => model.Person.MadrakID, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.DropDownListFor(model => model.Person.MadrakID, new SelectList(Model.Madrak, "MadrakID", "Title"),"مدرک خود را انتخاب کنید")
                @Html.ValidationMessageFor(model => model.Person.MadrakID, "", new { @class = "text-danger" })
            </div>
        </div>




        <div class="form-group">
            @Html.LabelFor(model => model.Person.Address, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.EditorFor(model => model.Person.Address, new { htmlAttributes = new { @class = "form-control" } })
                @Html.ValidationMessageFor(model => model.Person.Address, "", new { @class = "text-danger" })
            </div>
        </div>

        <div class="form-group">
            @Html.LabelFor(model => model.Person.Image, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.EditorFor(model => model.Person.Image, new { htmlAttributes = new { @class = "form-control" } })
                @Html.ValidationMessageFor(model => model.Person.Image, "", new { @class = "text-danger" })
            </div>
        </div>

        <div class="form-group">
            @Html.LabelFor(model => model.Person.Email, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.EditorFor(model => model.Person.Email, new { htmlAttributes = new { @class = "form-control" } })
                @Html.ValidationMessageFor(model => model.Person.Email, "", new { @class = "text-danger" })
            </div>
        </div>

        <div class="form-group">
            @Html.LabelFor(model => model.Person.Stutus, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                <div class="checkbox">
                    @Html.EditorFor(model => model.Person.Stutus)
                    @Html.ValidationMessageFor(model => model.Person.Stutus, "", new { @class = "text-danger" })
                </div>
            </div>
        </div>

        <div class="form-group">
            <div class="col-md-offset-2 col-md-10">
                <input type="submit" value="Create" class="btn btn-default" />
            </div>
        </div>
    </div>
}

<div>
    @Html.ActionLink("Back to List", "Index")
</div>

ویومدل رو به صورت زیر ایجاد کردم :

namespace WebApplication1.ViewModels
{
    public class VM_AddPerson
    {
        public Person  Person { get; set; }

        public IEnumerable<City> City { get; set; }

        public IEnumerable<Madrak> Madrak { get; set; }

    }
}

وقتی بریک پوینت میگیرم اون فیلد هایی که تو اکشن پست هستند هیچکدوم مقدار نمیگیرند

و خطالی Object reference not set to an instance of an object. میده

لطفا کامل راهنمایی کنید .ممنون