Null Referenz Ausnahme nach POST

Question

Ich habe ein Formular, das einige Werte vom Modell bekommt. Im POST wird dann der eingegebene Datenbenutzer behandelt und der Benutzer wird zu einer anderen Seite umgeleitet. Jedes Mal, wenn ich das Formular poste, bekomme ich null-Referenz-Ausnahme. Wo mache ich einen Fehler?

Keine der anderen Fragen, die danach fragen, hat mein Problem nicht gelöst, deshalb frage ich nochmal nach meinem spezifischen Code.

Die exeptions sind bei foreach-Schleifen - Model.Cart, Model.ShippingOptionsm usw.

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

<h2>Checkout</h2> 
<table class="table"> 
    <thead> 
     <tr> 
      <td>#</td> 
      <td>Name</td> 
      <td>Quantity</td> 
      <td>Price</td> 
      <td>Total price</td> 
     </tr> 
    </thead> 
    @foreach (CartItem i in Model.Cart) 
    { 
     <tr> 
      <td>@Html.Action("ProductPosition", "Cart", new { item = i })</td> 
      <td>@i.Name</td> 
      <td>@i.Quantity</td> 
      <td>@i.Price €</td> 
      <td>@i.Total €</td> 
     </tr> 
    } 

</table> 
<h3>Total: @Html.Action("TotalPrice", "Cart") €</h3> 

@using (Html.BeginForm("Checkout", "Cart")) 
{ 
    @Html.AntiForgeryToken() 
    <h2>Address</h2> 
    <div class="form-group"> 
     @Html.LabelFor(m => m.Name) 
     @Html.TextBoxFor(m => m.Name, new { @class = "form-control" }) 
     @Html.ValidationMessageFor(m => m.Name) 
    </div> 
    <div class="form-group"> 
     @Html.LabelFor(m => m.Address) 
     @Html.TextBoxFor(m => m.Address, new { @class = "form-control" }) 
     @Html.ValidationMessageFor(m => m.Address) 
    </div> 
    <div class="form-group"> 
     @Html.LabelFor(m => m.City) 
     @Html.TextBoxFor(m => m.City, new { @class = "form-control" }) 
     @Html.ValidationMessageFor(m => m.City) 
    </div> 
    <div class="form-group"> 
     @Html.LabelFor(m => m.PostNumber) 
     @Html.TextBoxFor(m => m.PostNumber, new { @class = "form-control" }) 
     @Html.ValidationMessageFor(m => m.PostNumber) 
    </div> 
    <div class="form-group"> 
     @Html.LabelFor(m => m.State) 
     @Html.TextBoxFor(m => m.State, new { @class = "form-control" }) 
     @Html.ValidationMessageFor(m => m.State) 
    </div> 



    <h2>Shipping</h2> 
    foreach (var i in Model.ShippingOptions) 
    { 
     <div class="radio"> 
      @Html.RadioButtonFor(m => m.ShippingOption, i.Id) @i.Name - @i.Price € 
     </div> 
    } 
    @Html.ValidationMessageFor(m => m.ShippingOption); 

    <h2>Payment</h2> 
    foreach (var i in Model.PaymentOptions) 
    { 
     <div class="radio"> 
      @Html.RadioButtonFor(m => m.PaymentOption, i.Id) @i.Name 
     </div> 
    } 
    @Html.ValidationMessageFor(m => m.PaymentOption); 
    <button type="submit" class="btn btn-primary">Continue</button> 
} 
@section scripts 
{ 
    @Scripts.Render("~/bundles/jqueryval") 
} 

Controller:

public ActionResult Checkout() 
    { 
     if (Session["cart"] == null) 
      return RedirectToAction("Index"); 

     var checkout = new CheckoutViewModel() 
     { 
      Cart = (List<CartItem>)Session["cart"], 
      PaymentOptions = _context.PaymentOptions.ToList(), 
      ShippingOptions = _context.ShippingOptions.ToList() 
     }; 


     return View(checkout); 
    } 

    [HttpPost] 
    [ValidateAntiForgeryToken] 
    public ActionResult Checkout(CheckoutViewModel m) 
    { 
     if (!ModelState.IsValid) 
      return View(); 

     //TODO: handle data 

     return RedirectToAction("OrderSuccess"); 
    } 

Answer 1

Add Modell-Deklaration am Seitenanfang

@model CheckoutViewModel