对象引用未设置为对象的实例。（已编辑）

Question

在将应用程序发布到IIS 7（Windows Server 2008 R2）之后，我正在使用带有Identity 2的ASP.NET MVC 5.

Works找了一段时间（我认为在第一个Session到期后）我得到这个错误：

对象引用未设置为对象的实例。   描述：执行当前Web请求期间发生未处理的异常。请查看堆栈跟踪以获取有关错误及其源自代码的位置的更多信息。

异常详细信息：System.NullReferenceException：未将对象引用设置为对象的实例。

来源错误：

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.  

堆栈追踪：

[NullReferenceException: Object reference not set to an instance of an object.]
O8.WEB.Controllers.AccountController.Login(String returnUrl) +715
lambda_method(Closure , ControllerBase , Object[] ) +126

System.Web.Mvc.ReflectedActionDescriptor.Execute（ControllerContext controllerContext，IDictionary 2 parameters) +216 System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary 2个参数）+38    System.Web.Mvc.Async.AsyncControllerActionInvoker.b__39（IAsyncResult asyncResult，ActionInvocation innerInvokeState）+11    System.Web.Mvc.Async.WrappedAsyncResult 2.CallEndDelegate(IAsyncResult asyncResult) +138 System.Web.Mvc.Async.AsyncInvocationWithFilters.<InvokeActionMethodFilterAsynchronouslyRecursive>b__3d() +111 System.Web.Mvc.Async.<>c__DisplayClass46.<InvokeActionMethodFilterAsynchronouslyRecursive>b__3f() +452 System.Web.Mvc.Async.<>c__DisplayClass33.<BeginInvokeActionMethodWithFilters>b__32(IAsyncResult asyncResult) +15 System.Web.Mvc.Async.<>c__DisplayClass2b.<BeginInvokeAction>b__1c() +32 System.Web.Mvc.Async.<>c__DisplayClass21.<BeginInvokeAction>b__1e(IAsyncResult asyncResult) +231 System.Web.Mvc.Controller.<BeginExecuteCore>b__1d(IAsyncResult asyncResult, ExecuteCoreState innerState) +29 System.Web.Mvc.Async.WrappedAsyncVoid 1.CallEndDelegate（IAsyncResult asyncResult）+111    System.Web.Mvc.Controller.EndExecuteCore（IAsyncResult asyncResult）+53    System.Web.Mvc.Async.WrappedAsyncVoid 1.CallEndDelegate(IAsyncResult asyncResult) +19 System.Web.Mvc.MvcHandler.<BeginProcessRequest>b__5(IAsyncResult asyncResult, ProcessRequestState innerState) +51 System.Web.Mvc.Async.WrappedAsyncVoid 1.CallEndDelegate（IAsyncResult asyncResult）+111    System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute（）+606    System.Web.HttpApplication.ExecuteStep（IExecutionStep step，Boolean＆amp; completedSynchronously）+288

修改 当我使用Visual Studio的调试器时，没有发生此错误。它只发生在我部署到IIS之后。