列ID在规范中出现多次

最近我又开始了我的EF 4.1/MVC 3项目，并开始构建实际的前端功能。

现在我正在开发一个"简单"的消息系统，但当我转到该页面时，我得到了标题中所述的错误

编辑

它创建数据库而不是模型。

堆栈跟踪：

[NullReferenceException:对象引用未设置为对象。]ASP_中的Page_Views_Inbox_Index_shtml.Execute（）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（WebPageContextpageContext，TextWriter编写器，WebPageRenderingBase startPage）+76
System.Web.Mvc.RazorView.RenderView（ViewContext-ViewContext，TextWriter编写器，对象实例）+222
System.Web.Mvc.BuildManagerCompiledView.RRender（ViewContextviewContext，TextWriter编写器）+115
System.Web.Mvc.ViewResultBase.ExecuteResult（ControllerContext上下文）+295 System.Web.Mvc.ControllerActionInvoker.InvokeActionResult（ControllerContextcontrollerContext，ActionResult ActionResult）+13
System.Web.Mvc.<>c_显示类1c.b_19（）+23 System.Web.Mvc.ControllerActionInvoker.IInvokeActionResultFilter（IResultFilterfilter，ResultExecutingContext preContext，Func 1 continuation) +242
System.Web.Mvc.<>c__DisplayClass1e.<InvokeActionResultWithFilters>b__1b() +21 System.Web.Mvc.ControllerActionInvoker.InvokeActionResultWithFilters(ControllerContext controllerContext, IList 1 filter，ActionResult ActionResult）+177
System.Web.Mvc.ControllerActionInvoker.InvokeAction（ControllerContextcontrollerContext，字符串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（RequestContextrequestContext）+10
System.Web.Mvc.<>c_显示类b.b_5（）+34
System.Web.Mvc.Async。<>c_显示类1.b_0（）+19
System.Web.Mvc.Async。<>c_DisplayClass8 1.<BeginSynchronous>b__7(IAsyncResult _) +10 System.Web.Mvc.Async.WrappedAsyncResult 1.End（）+62 System.Web.Mvc.<>c_DisplayClasse.b_d（）+48
System.Web.Mvc.SecurityUtil.b_0（操作f）+7System.Web.Mvc.SecurityUtil.ProcessInApplicationTrust（操作操作）+22 System.Web.Mvc.MvcHandler.EndProcessRequest（IAsyncResult-asyncResult）+60
System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.EndProcessRequest（IAsyncResult结果）+9
System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute（）+9478661 System.Web.HttpApplication.ExecuteStep（IExecutionStep步骤，Boolean和completedSynchronously）+178

内部异常：｛"列ID在规范中出现多次。"｝

最近添加的代码是.

控制器：

//
// 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();
}

型号

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);

有人知道我为什么会犯那个错误吗？在我添加这些类之前，它运行良好。