C# LINQ to实体返回“对象引用未设置为对象实例”
我有一段代码，它使用名为RESOURCE_V的视图检查用户是否在我们的数据库中。如果没有，代码使用实体框架使用Active Directory中的用户信息将用户添加到数据库中。然后，我想重新查询资源视图以获取提交的信息。这样做时，我得到的对象引用未设置为对象的实例。。以下是完整的代码：C# LINQ to实体返回“对象引用未设置为对象实例”,c#,linq,entity-framework,linq-to-entities,C#,Linq,Entity Framework,Linq To Entities,我有一段代码，它使用名为RESOURCE_V的视图检查用户是否在我们的数据库中。如果没有，代码使用实体框架使用Active Directory中的用户信息将用户添加到数据库中。然后，我想重新查询资源视图以获取提交的信息。这样做时，我得到的对象引用未设置为对象的实例。。以下是完整的代码： HALEntities context = new HALEntities(); List<RESOURCE_V> userData = (from i in context.
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();
}
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()
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引起的。如果我在查询中硬编码另一个ID，它将工作，并且不会抛出错误。我已确定新ID实际上正在添加到数据库中。该实体有一个复合键，保存新实体时，其中一个键列为空。EF不支持它抛出的可为null的键，但显然EF中存在一个bug，在这个特定场景中没有检查这个条件，因此NRE。您需要确保在主键列中没有返回空值 我也有同样的问题。集合类型的“我的类”字段为空。我费了很大劲才解决这个问题。 最后一个错误是输入错误——我在为类字段名进行局部声明时使用new创建对象，然后它超出了局部范围。 我知道它并没有回答这个问题，但作为一个要点，我们需要重新检查代码中是否存在此类错误。
抱歉，我真的很想帮助像我这样的人解决类似的问题。如果userData.Count==0，而不是userData.Count>0，你不想吗？堆栈跟踪是什么？我相信它无法执行ToList语句，可能是查询出了问题，尤其是在view@Sayse：如果context.RESOURCE_V是EntityFramework集合，则该集合将由EntityFramework计算，因此i不能为null。因为他在这一点之前使用了context.RESOURCE_V`s，所以很明显这不是空的。在这个stacktrace中没有EF。如果问题是由EF引起的，则需要显示InnerExceptions（如果有）。
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()
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