Cannot perform runtime binding on a null reference, But it is NOT a null reference

Question

using: MVC 4, ASP.NET Razor

I'm getting an error that looks like it shouldn't be possible. It tells me that i'm using a null-reference, States, but clearly it is being set.

Controller:

public ActionResult Index()
{
    Dictionary<int, string> states = new Dictionary<int, string>()
    {
        { -1, "a"},
        { 0, "b"},
        { 1, "c"},
        { 2, "d"},
    };

    //assigning states
    ViewBag.States = states;

    foreach (KeyValuePair<int, string> de in ViewBag.States)
    {
        Debug.WriteLine(de.Key);
    }
    return View();
}

The View:

<div class="search-input">
    <select>
        @foreach (KeyValuePair<int, string> de in ViewBag.States)
        {
            <option value="@de.Key">@de.Value</option>
        }
    </select>
</div>

The error:

Cannot perform runtime binding on a null reference
Line 54: @foreach (KeyValuePair<int, string> de in ViewBag.States)

Answer 1

Found solution: I had typo in my view, ViewBag.Typo <-- this caused the error, but the debugger placed the exception at a irrelevant place.

Answer 2

This error happens when you have a ViewBag Non-Existent in your razor code calling a method.

Controller

public ActionResult Accept(int id)
{
    return View();
}

razor:

<div class="form-group">
      @Html.LabelFor(model => model.ToId, "To", htmlAttributes: new { @class = "control-label col-md-2" })
     <div class="col-md-10">
           @Html.Flag(Model.from)
     </div>
</div>
<div class="form-group">
     <div class="col-md-10">
          <input value="@ViewBag.MaximounAmount.ToString()" />@* HERE is the error *@ 
     </div>
</div>

For some reason, the .net aren't able to show the error in the correct line.

Normally this causes a lot of wasted time.

Answer 3

This exception is also thrown when a non-existent property is being updated dynamically, using reflection.

If one is using reflection to dynamically update property values, it's worth checking to make sure the passed PropertyName is identical to the actual property.

In my case, I was attempting to update Employee.firstName, but the property was actually Employee.FirstName.

Worth keeping in mind. :)