오류입니다.

요청을 처리하는 동안 오류가 발생했습니다.

System.NullReferenceException: 개체 참조가 개체의 인스턴스로 설정되지 않았습니다. 위치: StudentV21.Controllers.RankingController.RankingPointsMonthly() 파일 D:\Project2\Private\StudentV21\StudentV21\Controllers\RankingController.cs:줄 1541 위치: lambda_method(Closure , ControllerBase , Object[] ) 위치: System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext controllerContext, IDictionary`2 parameters) 위치: System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary`2 parameters) 위치: System.Web.Mvc.Async.AsyncControllerActionInvoker.<BeginInvokeSynchronousActionMethod>b__36(IAsyncResult asyncResult, ActionInvocation innerInvokeState) 위치: System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResult`2.CallEndDelegate(IAsyncResult asyncResult) 위치: System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethod(IAsyncResult asyncResult) 위치: System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<InvokeActionMethodFilterAsynchronouslyRecursive>b__3c() 위치: System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<>c__DisplayClass45.<InvokeActionMethodFilterAsynchronouslyRecursive>b__3e() 위치: System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethodWithFilters(IAsyncResult asyncResult) 위치: System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass1e.<>c__DisplayClass28.<BeginInvokeAction>b__19() 위치: System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass1e.<BeginInvokeAction>b__1b(IAsyncResult asyncResult)