LINQ to Entitys return“；对象引用未设置为对象的实例&”；
本文关键字：对象 实例 设置 Entitys to return 对象引用 LINQ | 更新日期: 2023-09-27 17:58:52
我有一段代码，它使用一个名为RESOURCE_V的视图来检查用户是否在我们的数据库中。如果没有，代码将使用实体框架使用Active Directory中的用户信息将用户添加到数据库中。然后我想重新查询RESOURCE_V视图以获得提交的信息。在这样做的时候，我得到了"对象引用没有设置为对象的实例"
HALEntities context = new HALEntities();
List<RESOURCE_V> userData = (from i in context.RESOURCE_V
where i.NT_USER_N == Environment.UserName
select i).ToList();
// add user to RSRC table using Active Directory details
if (userData.Count > 0)
{
PrincipalContext principleContext = new PrincipalContext(ContextType.Domain, HAL_Globals.domain);
UserPrincipal user = UserPrincipal.FindByIdentity(principleContext, IdentityType.SamAccountName, HAL_Globals.domain + "''" + Environment.UserName);
RSRC rsrc = new RSRC();
rsrc.RSRC_I = context.RSRCs.Select(u => u.RSRC_I).Max() + 1;
rsrc.NT_USER_N = user.SamAccountName + "AAAA";
rsrc.FRST_N = user.GivenName;
rsrc.LAST_N = user.Surname;
rsrc.INIL_N = (user.MiddleName == null) ? "X" : user.MiddleName.Substring(0, 1);
rsrc.SHRT_N = user.GivenName.Substring(0, 1) + ((user.MiddleName == null) ? "X" : user.MiddleName.Substring(0, 1)) + user.Surname.Substring(0, 1);
rsrc.EMAIL_I = user.EmailAddress;
rsrc.TELE_I = user.VoiceTelephoneNumber.Replace("(", "").Replace(")", "").Replace("-", "");
rsrc.ACTV_F = true;
rsrc.CRTE_USER_I = Environment.UserName;
rsrc.CRTE_TS = DateTime.Now;
rsrc.UPDT_USER_I = Environment.UserName;
rsrc.UPDT_TS = DateTime.Now;
context.RSRCs.Add(rsrc);
context.SaveChanges();
userData = (from i in context.RESOURCE_V
where i.NT_USER_N == Environment.UserName + "AAAA"
select i).ToList();
}
请注意，逻辑与我的描述不完全匹配，因为我正在使用此代码对已经存在的ID进行测试。出错的行是if块中的最后一条语句：
userData = (from i in context.RESOURCE_V
where i.NT_USER_N == Environment.UserName + "AAAA"
select i).ToList();
我尝试过使用不同的LINQ语法重新创建实体上下文，但没有成功。如有任何帮助，我们将不胜感激。
编辑：
根据请求，这里是堆栈跟踪：
at System.RuntimeTypeHandle.CreateInstance(RuntimeType type, Boolean publicOnly, Boolean noCheck, Boolean& canBeCached, RuntimeMethodHandleInternal& ctor, Boolean& bNeedSecurityCheck)
at System.RuntimeType.CreateInstanceSlow(Boolean publicOnly, Boolean skipCheckThis, Boolean fillCache, StackCrawlMark& stackMark)
at System.RuntimeType.CreateInstanceDefaultCtor(Boolean publicOnly, Boolean skipCheckThis, Boolean fillCache, StackCrawlMark& stackMark)
at System.Activator.CreateInstance(Type type, Boolean nonPublic)
at System.RuntimeType.CreateInstanceImpl(BindingFlags bindingAttr, Binder binder, Object[] args, CultureInfo culture, Object[] activationAttributes, StackCrawlMark& stackMark)
at System.Activator.CreateInstance(Type type, BindingFlags bindingAttr, Binder binder, Object[] args, CultureInfo culture, Object[] activationAttributes)
at System.Activator.CreateInstance(Type type, Object[] args)
at System.Xaml.Schema.SafeReflectionInvoker.CreateInstanceCritical(Type type, Object[] arguments)
at System.Xaml.Schema.SafeReflectionInvoker.CreateInstance(Type type, Object[] arguments)
at System.Xaml.Schema.XamlTypeInvoker.CreateInstance(Object[] arguments)
at MS.Internal.Xaml.Runtime.ClrObjectRuntime.CreateInstanceWithCtor(XamlType xamlType, Object[] args)
at MS.Internal.Xaml.Runtime.ClrObjectRuntime.CreateInstance(XamlType xamlType, Object[] args)
at MS.Internal.Xaml.Runtime.PartialTrustTolerantRuntime.CreateInstance(XamlType xamlType, Object[] args)
at System.Xaml.XamlObjectWriter.Logic_CreateAndAssignToParentStart(ObjectWriterContext ctx)
at System.Xaml.XamlObjectWriter.WriteStartMember(XamlMember property)
at System.Xaml.XamlWriter.WriteNode(XamlReader reader)
at System.Windows.Markup.WpfXamlLoader.TransformNodes(XamlReader xamlReader, XamlObjectWriter xamlWriter, Boolean onlyLoadOneNode, Boolean skipJournaledProperties, Boolean shouldPassLineNumberInfo, IXamlLineInfo xamlLineInfo, IXamlLineInfoConsumer xamlLineInfoConsumer, XamlContextStack`1 stack, IStyleConnector styleConnector)
at System.Windows.Markup.WpfXamlLoader.Load(XamlReader xamlReader, IXamlObjectWriterFactory writerFactory, Boolean skipJournaledProperties, Object rootObject, XamlObjectWriterSettings settings, Uri baseUri)
at System.Windows.Markup.WpfXamlLoader.LoadBaml(XamlReader xamlReader, Boolean skipJournaledProperties, Object rootObject, XamlAccessLevel accessLevel, Uri baseUri)
at System.Windows.Markup.XamlReader.LoadBaml(Stream stream, ParserContext parserContext, Object parent, Boolean closeStream)
at System.Windows.Application.LoadBamlStreamWithSyncInfo(Stream stream, ParserContext pc)
at System.Windows.Application.LoadComponent(Uri resourceLocator, Boolean bSkipJournaledProperties)
at System.Windows.Application.DoStartup()
at System.Windows.Application.<.ctor>b__1(Object unused)
at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
at MS.Internal.Threading.ExceptionFilterHelper.TryCatchWhen(Object source, Delegate method, Object args, Int32 numArgs, Delegate catchHandler)
at System.Windows.Threading.DispatcherOperation.InvokeImpl()
at System.Windows.Threading.DispatcherOperation.InvokeInSecurityContext(Object state)
at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Windows.Threading.DispatcherOperation.Invoke()
at System.Windows.Threading.Dispatcher.ProcessQueue()
at System.Windows.Threading.Dispatcher.WndProcHook(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
at MS.Win32.HwndWrapper.WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
at MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o)
at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
at MS.Internal.Threading.ExceptionFilterHelper.TryCatchWhen(Object source, Delegate method, Object args, Int32 numArgs, Delegate catchHandler)
at System.Windows.Threading.Dispatcher.LegacyInvokeImpl(DispatcherPriority priority, TimeSpan timeout, Delegate method, Object args, Int32 numArgs)
at MS.Win32.HwndSubclass.SubclassWndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam)
at MS.Win32.UnsafeNativeMethods.DispatchMessage(MSG& msg)
at System.Windows.Threading.Dispatcher.PushFrameImpl(DispatcherFrame frame)
at System.Windows.Threading.Dispatcher.PushFrame(DispatcherFrame frame)
at System.Windows.Threading.Dispatcher.Run()
at System.Windows.Application.RunDispatcher(Object ignore)
at System.Windows.Application.RunInternal(Window window)
at System.Windows.Application.Run(Window window)
at System.Windows.Application.Run()
at HAL.App.Main() in c:'HAL'HAL_PROD'HAL'obj'Debug'App.g.cs:line 0
at System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args)
at System.AppDomain.nExecuteAssembly(RuntimeAssembly assembly, String[] args)
at System.Runtime.Hosting.ManifestRunner.Run(Boolean checkAptModel)
at System.Runtime.Hosting.ManifestRunner.ExecuteAsAssembly()
at System.Runtime.Hosting.ApplicationActivator.CreateInstance(ActivationContext activationContext, String[] activationCustomData)
at System.Runtime.Hosting.ApplicationActivator.CreateInstance(ActivationContext activationContext)
at System.Activator.CreateInstance(ActivationContext activationContext)
at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssemblyDebugInZone()
at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Threading.ThreadHelper.ThreadStart()
编辑2:内部异常堆栈跟踪：
at System.Data.EntityKey.AddHashValue(Int32 hashCode, Object keyValue)
at System.Data.EntityKey.GetHashCode()
at System.Collections.Generic.GenericEqualityComparer`1.GetHashCode(T obj)
at System.Collections.Generic.Dictionary`2.FindEntry(TKey key)
at System.Collections.Generic.Dictionary`2.TryGetValue(TKey key, TValue& value)
at System.Data.Objects.ObjectStateManager.TryGetEntityEntry(EntityKey key, EntityEntry& entry)
at System.Data.Common.Internal.Materialization.Shaper.HandleEntityAppendOnly[TEntity](Func`2 constructEntityDelegate, EntityKey entityKey, EntitySet entitySet)
at lambda_method(Closure , Shaper )
at System.Data.Common.Internal.Materialization.Coordinator`1.ReadNextElement(Shaper shaper)
at System.Data.Common.Internal.Materialization.Shaper`1.SimpleEnumerator.MoveNext()
at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
at HAL.HAL_CurrentUser..ctor(SqlConnection currentServerConnection) in c:'HAL'HAL_PROD'HAL'Global Classes'HAL_CurrentUser.cs:line 86
at HAL.HAL_CurrentUser.get_Instance() in c:'HAL'HAL_PROD'HAL'Global Classes'HAL_CurrentUser.cs:line 46
at HAL.WelcomeViewModel..ctor() in c:'HAL'HAL_PROD'HAL'HAL Classes'Welcome'WelcomeViewModel.cs:line 21
at HAL.Welcome..ctor() in c:'HAL'HAL_PROD'HAL'HAL Classes'Welcome'Welcome.xaml.cs:line 26
at HAL.Navigation..ctor() in c:'HAL'HAL_PROD'HAL'Navigation.xaml.cs:line 17
编辑3:
在处理了第二个LINQ查询中查询的值之后，我确定问题是由我在LINQ查询的where子句中过滤新ID这一事实引起的。如果我在查询中硬编码另一个ID，它就会工作，并且不会引发错误。我已经确定新的ID实际上正在添加到数据库中。
实体有一个复合键，保存新实体时，其中一个键列为null。EF不支持可为null的密钥（它抛出），但显然EF中有一个错误，在这个特定的场景中没有检查这个条件，因此也没有检查NRE。您需要确保主键列中没有返回null值。
我也遇到了同样的问题。集合类型的类字段为空。我费了很大劲才解决这个问题。最后，错误是打字错误——我用new创建对象，同时为类字段名进行本地声明，然后它超出了本地范围。我知道它不能回答这个主题，但作为一个要点，重新检查代码中是否存在此类错误。对不起，我真的很想帮助其他像我一样的人解决类似的问题。