Question

Since I upgraded from MVC 2 to MVC 3 RC, using TryUpdateModel causes a NullReferenceException. This problem only occurs when running my action method as part of a unit test. Running it on the actual server works as expected.

Here’s a stack trace of the exception:

System.NullReferenceException: Object
reference not set to an instance of an
object. at
System.Web.Mvc.JsonValueProviderFactory.GetValueProvider(ControllerContext
controllerContext) at
System.Web.Mvc.ValueProviderFactoryCollection.<>c_DisplayClassc.b_7(ValueProviderFactory
factory) at
System.Linq.Enumerable.WhereSelectEnumerableIterator2.MoveNext()
at
System.Linq.Enumerable.WhereSelectEnumerableIterator2.MoveNext()
at
System.Collections.Generic.List1..ctor(IEnumerable1
collection) at
System.Linq.Enumerable.ToList[TSource](IEnumerable`1
source) at
System.Web.Mvc.ValueProviderFactoryCollection.GetValueProvider(ControllerContext
controllerContext) at
System.Web.Mvc.Controller.TryUpdateModel[TModel](TModel
model, String prefix)
… my own code from here on….

In case it matters, my controller has the following signature:

[AcceptVerbs(HttpVerbs.Post)]
public virtual ActionResult Edit(int id, FormCollection collection)
{
}

My guess is that this has to do with the new way DI works in MVC3, but I can’t figure out what I’m doing wrong. Perhaps there is something in terms of DI setup that is required in MVC 3, but wasn’t required in MVC 2?

Answer 1

In case someone else has the same problem and finds this post:

I solved the problem generically based on Ivan Kortym’s answer (thanks!), with the following piece of code in my controller base class constructor:

if (Request!=null && Request.Form != null && Request.Form.HasKeys() && ValueProvider == null)
{
    ValueProvider = new FormCollection(Request.Form).ToValueProvider();
}