Question

Recently i’ve picked up my EF 4.1 / MVC 3 project again and started building in actual frontend capabilities.

Now i’m developing a “simple” message system but upon going to that page i get the error as stated in the title

EDIT

It creates the database just not the models.

Stack trace:

[NullReferenceException: Object reference not set to an instance of an
object.] ASP._Page_Views_Inbox_Index_cshtml.Execute() in
c:\Development\MVC\DOCCL\Views\Inbox\Index.cshtml:18
System.Web.WebPages.WebPageBase.ExecutePageHierarchy() +197
System.Web.Mvc.WebViewPage.ExecutePageHierarchy() +81
System.Web.WebPages.StartPage.RunPage() +17
System.Web.WebPages.StartPage.ExecutePageHierarchy() +62
System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext
pageContext, TextWriter writer, WebPageRenderingBase startPage) +76
System.Web.Mvc.RazorView.RenderView(ViewContext viewContext,
TextWriter writer, Object instance) +222
System.Web.Mvc.BuildManagerCompiledView.Render(ViewContext
viewContext, TextWriter writer) +115
System.Web.Mvc.ViewResultBase.ExecuteResult(ControllerContext context)
+295 System.Web.Mvc.ControllerActionInvoker.InvokeActionResult(ControllerContext
controllerContext, ActionResult actionResult) +13
System.Web.Mvc.<>c_DisplayClass1c.b_19()
+23 System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilter(IResultFilter
filter, ResultExecutingContext preContext, Func1 continuation) +242
System.Web.Mvc.<>c__DisplayClass1e.<InvokeActionResultWithFilters>b__1b()
+21 System.Web.Mvc.ControllerActionInvoker.InvokeActionResultWithFilters(ControllerContext
controllerContext, IList1 filters, ActionResult actionResult) +177
System.Web.Mvc.ControllerActionInvoker.InvokeAction(ControllerContext
controllerContext, String actionName) +324
System.Web.Mvc.Controller.ExecuteCore() +106
System.Web.Mvc.ControllerBase.Execute(RequestContext requestContext)
+91 System.Web.Mvc.ControllerBase.System.Web.Mvc.IController.Execute(RequestContext
requestContext) +10
System.Web.Mvc.<>c_DisplayClassb.b_5() +34
System.Web.Mvc.Async.<>c_DisplayClass1.b_0() +19
System.Web.Mvc.Async.<>c_DisplayClass81.<BeginSynchronous>b__7(IAsyncResult
_) +10 System.Web.Mvc.Async.WrappedAsyncResult1.End() +62 System.Web.Mvc.<>c_DisplayClasse.b_d() +48
System.Web.Mvc.SecurityUtil.b_0(Action f) +7
System.Web.Mvc.SecurityUtil.ProcessInApplicationTrust(Action action)
+22 System.Web.Mvc.MvcHandler.EndProcessRequest(IAsyncResult asyncResult) +60
System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.EndProcessRequest(IAsyncResult
result) +9
System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
+9478661 System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +178

InnerException :
{“A column ID occurred more than once in the specification.”}

The recently added code is.

Controller:

//
// GET: /Inbox/Index/5/1
public ActionResult Index(int? Id, int Page = 1)
{
    try
    {
        const int pageSize = 10;
        var messages = from m in horseTracker.Messages
                        where m.ReceiverId.Equals(Id)
                        select m;

        var paginatedMessages = new PaginatedList<Message>(messages, Page, pageSize);

        return View(paginatedMessages);
    }
    catch (Exception ex)
    {

    }
    return View();
}

Models

public class Message
{
    [Key]
    public int Id { get; set; }

    [Required(ErrorMessage = "Subject is required")]
    [Display(Name = "Subject")]
    public string Subject { get; set; }

    [Required(ErrorMessage = "Message is required")]
    [Display(Name = "Message")]
    public string Content { get; set; }

    [Required]
    [Display(Name = "Date")]
    public DateTime Created { get; set; }

    public Boolean Read { get; set; }

    [Required(ErrorMessage = "Can't create a message without a user")]
    public int SenderId { get; set; }
    public virtual User Sender { get; set; }

    [Required(ErrorMessage = "Please pick a recipient")]
    public int ReceiverId { get; set; }
    public virtual User Receiver { get; set; }
}

public class User
{
    [Key]
    public int Id { get; set; }

    [Required]
    [Display(Name = "Username")]
    public string UserName { get; set; }

    [Required]
    [Display(Name = "First Name")]
    public string FirstName { get; set; }

    [Required]
    [Display(Name = "Last Name")]
    public string LastName { get; set; }

    [Required]
    [Display(Name = "E-Mail")]
    public string Email { get; set; }

    [Required]
    [Display(Name = "Password")]
    public string Password { get; set; }

    [Required]
    [Display(Name = "Country")]
    public string Country { get; set; }

    public string EMail { get; set; }

    //Races
    public virtual ICollection<Message> Messages { get; set; }
}

modelBuilder.Entity<User>()
    .HasMany(u => u.Messages)
    .WithRequired(m => m.Receiver)
    .HasForeignKey(m => m.ReceiverId)
    .WillCascadeOnDelete(false);

Anyone have a clue on why i might be getting that error?
Before i added these classes it was working fine.

Answer 1

In your Message Model, Id is not nullable, but your action allows nulls, EF cant match these two types up in the where clause in your query & throw an exception.