@ Html.AntiForgeryToken（）随机引发NullReferenceException

Question

我的许多Web应用程序中都有@ Html.AntiForgeryToken（）。它在大多数时间都有效，但有时却无效。失败的方式各不相同。但是，我只关注一种情况。在这种情况下，它将引发NullReferenceException。

调试器显示Html不为null。虽然，我不知道它怎么可能为空。无论如何，我什么也看不到。堆栈跟踪指示异常是从.Net的深层引发的。总的来说，这很难调试，因为我不得不单击数小时才能决定再次失败。

关于可能导致此问题或如何解决此问题的任何想法。

怎么了？

Exception: System.NullReferenceException
Object reference not set to an instance of an object.
   at System.Security.Claims.Claim.get_Type()
   at System.Web.Helpers.Claims.Claim.ClaimFactory`1.Create(TClaim claim)
   at System.Web.Helpers.Claims.Claim.Create[TClaim](TClaim claim)
   at System.Linq.Enumerable.WhereSelectEnumerableIterator`2.MoveNext()
   at System.Linq.Enumerable.SingleOrDefault[TSource](IEnumerable`1 source, Func`2 predicate)
   at System.Web.Helpers.AntiXsrf.ClaimUidExtractor.GetUniqueIdentifierParameters(ClaimsIdentity claimsIdentity, String uniqueClaimTypeIdentifier)
   at System.Web.Helpers.AntiXsrf.ClaimUidExtractor.ExtractClaimUid(IIdentity identity)
   at System.Web.Helpers.AntiXsrf.TokenValidator.GenerateFormToken(HttpContextBase httpContext, IIdentity identity, AntiForgeryToken cookieToken)
   at System.Web.Helpers.AntiXsrf.AntiForgeryWorker.GetTokens(HttpContextBase httpContext, AntiForgeryToken oldCookieToken, AntiForgeryToken& newCookieToken, AntiForgeryToken& formToken)
   at System.Web.Helpers.AntiXsrf.AntiForgeryWorker.GetFormInputElement(HttpContextBase httpContext)
   at System.Web.Helpers.AntiForgery.GetHtml()
   at System.Web.Mvc.HtmlHelper.AntiForgeryToken()
   at ASP._Page_Views_Shared__Layout_cshtml.Execute() in C:\Code\Communication Screens\StudentNeeds\WebApp\Views\Shared\_Layout.cshtml:line 34
   at System.Web.WebPages.WebPageBase.ExecutePageHierarchy()
   at System.Web.Mvc.WebViewPage.ExecutePageHierarchy()
   at System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage)
   at System.Web.WebPages.WebPageBase.<>c__DisplayClass40_0.<RenderPageCore>b__0(TextWriter writer)
   at System.Web.WebPages.HelperResult.WriteTo(TextWriter writer)
   at System.Web.WebPages.WebPageBase.Write(HelperResult result)
   at System.Web.WebPages.WebPageBase.RenderSurrounding(String partialViewName, Action`1 body)
   at System.Web.WebPages.WebPageBase.PopContext()
   at System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage)
   at System.Web.Mvc.RazorView.RenderView(ViewContext viewContext, TextWriter writer, Object instance)
   at System.Web.Mvc.BuildManagerCompiledView.Render(ViewContext viewContext, TextWriter writer)
   at System.Web.Mvc.ViewResultBase.ExecuteResult(ControllerContext context)
   at System.Web.Mvc.ControllerActionInvoker.InvokeActionResult(ControllerContext controllerContext, ActionResult actionResult)
   at System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilterRecursive(IList`1 filters, Int32 filterIndex, ResultExecutingContext preContext, ControllerContext controllerContext, ActionResult actionResult)
   at System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilterRecursive(IList`1 filters, Int32 filterIndex, ResultExecutingContext preContext, ControllerContext controllerContext, ActionResult actionResult)

谢谢， 斯凯