title: Null interface in the constructor
body: <p>I have a ASP.NET MVC application and I'm using MEF to import my interfaces. The problem is that my <code>IVotesRepository</code> interface is null when it's passed to the constructor.</p>
  
  <p>Here is the code from my controller:</p>
  
  <pre><code>public class VotesController : BaseController
  {
      //
      // GET: /Votes/
      IVotesRepository VotesRepository;
      IAccountRepository accountRepository;
  
      public VotesController(IVotesRepository votesRepo, IAccountRepository accountRepo)
      {
          VotesRepository = votesRepo;
          accountRepository = accountRepo;
      }
  </code></pre>
  
  <p>And here is the interface and the repository itself:</p>
  
  <pre><code>public interface IVotesRepository
  {
      void SaveVotes(int TeamId, int GameId, int UserId);
  
      bool CheckIfUserHaveVoted(int UserId, int GameId);
  }
  
  [Export(typeof(IVotesRepository))]
  public class VotesRepository : IVotesRepository
  {
     ...
  }
  </code></pre>
  
  <p>Why is the <code>IVotesRepository</code> instance null?</p>
  
  <p>EDIT: </p>
  
  <p>Stack trace:</p>
  
  <pre><code>Object reference not set to an instance of an object at SocialSport.Controllers.VotesController.SaveVotes(Nullable`1 TeamId, Nullable`1 GameId) in C:\...\Visual Studio 2010\Projects\SocialSport\Implementation\Source\SocialSportWeb\Controllers\VotesController.cs:line 29
     at lambda_method(Closure , ControllerBase , Object[] )
     at System.Web.Mvc.ActionMethodDispatcher.Execute(ControllerBase controller, Object[] parameters)
     at System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext controllerContext, IDictionary`2 parameters)
     at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary`2 parameters)
     at System.Web.Mvc.ControllerActionInvoker.&lt;&gt;c__DisplayClass15.&lt;InvokeActionMethodWithFilters&gt;b__12()
     at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodFilter(IActionFilter filter, ActionExecutingContext preContext, Func`1 continuation)
  </code></pre>