当属性设置程序为内部时，ADO.NET数据服务实体框架请求错误

Question

在使用实体框架数据模型公开ADO.NET数据服务时，我收到一条错误消息，该实体框架数据模型包含一个在属性上具有内部设置器的实体(称为"Case")。如果我将setter修改为public (使用实体设计器)，数据服务就可以正常工作。

我不需要在数据服务中公开实体“案例”，因此我尝试限制使用SetEntitySetAccessRule公开的实体。这不起作用，服务端点失败，并出现相同的错误。

public static void InitializeService(IDataServiceConfiguration config)
{
    config.SetEntitySetAccessRule("User", EntitySetRights.AllRead);
}

调用.svc终结点时，浏览器中会报告该错误消息。它非常通用，上面写着“请求错误。服务器在处理请求时遇到错误。有关详细信息，请参阅服务器日志。“遗憾的是，系统和应用程序事件日志中没有条目。

我找到了这个stackoverflow question，它展示了如何在服务上配置跟踪。执行此操作后，跟踪日志中报告了以下NullReferenceExceptoin错误。

当包含一个带有内部setter的实体时，有人知道如何避免这个异常吗？

<E2ETraceEvent xmlns="http://schemas.microsoft.com/2004/06/E2ETraceEvent">
<System xmlns="http://schemas.microsoft.com/2004/06/windows/eventlog/system">
<EventID>131076</EventID>
<Type>3</Type>
<SubType Name="Error">0</SubType>
<Level>2</Level>
<TimeCreated SystemTime="2008-11-05T22:30:44.1523578Z" />
<Source Name="System.ServiceModel" />
<Correlation ActivityID="{da77ee97-960f-4275-a5e7-a181c0b024b1}" />
<Execution ProcessName="WebDev.WebServer" ProcessID="6388" ThreadID="8" />
<Channel />
<Computer>MOTOJIM</Computer>
</System>
<ApplicationData>
<TraceData>
<DataItem>
<TraceRecord xmlns="http://schemas.microsoft.com/2004/10/E2ETraceEvent/TraceRecord" Severity="Error">
<TraceIdentifier>http://msdn.microsoft.com/en-US/library/System.ServiceModel.Diagnostics.TraceHandledException.aspx</TraceIdentifier>
<Description>Handling an exception.</Description>
<AppDomain>685a2910-19-128703978432492675</AppDomain>
<Exception>
<ExceptionType>System.NullReferenceException, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</ExceptionType>
<Message>Object reference not set to an instance of an object.</Message>
<StackTrace>
at System.Data.Services.Providers.ObjectContextServiceProvider.PopulateMemberMetadata(ResourceType resourceType, MetadataWorkspace workspace, IDictionary`2 entitySets, IDictionary`2 knownTypes)
at System.Data.Services.Providers.ObjectContextServiceProvider.PopulateMetadata(IDictionary`2 knownTypes, IDictionary`2 entitySets)
at System.Data.Services.Providers.BaseServiceProvider.PopulateMetadata()
at System.Data.Services.DataService`1.CreateProvider(Type dataServiceType, Object dataSourceInstance, DataServiceConfiguration&amp; configuration)
at System.Data.Services.DataService`1.EnsureProviderAndConfigForRequest()
at System.Data.Services.DataService`1.ProcessRequestForMessage(Stream messageBody)
at SyncInvokeProcessRequestForMessage(Object , Object[] , Object[] )
at System.ServiceModel.Dispatcher.SyncMethodInvoker.Invoke(Object instance, Object[] inputs, Object[]&amp; outputs)
at System.ServiceModel.Dispatcher.DispatchOperationRuntime.InvokeBegin(MessageRpc&amp; rpc)
at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage5(MessageRpc&amp; rpc)
at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage4(MessageRpc&amp; rpc)
at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage3(MessageRpc&amp; rpc)
at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage2(MessageRpc&amp; rpc)
at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage1(MessageRpc&amp; rpc)
at System.ServiceModel.Dispatcher.MessageRpc.Process(Boolean isOperationContextSet)
</StackTrace>
<ExceptionString>System.NullReferenceException: Object reference not set to an instance of an object.
   at System.Data.Services.Providers.ObjectContextServiceProvider.PopulateMemberMetadata(ResourceType resourceType, MetadataWorkspace workspace, IDictionary`2 entitySets, IDictionary`2 knownTypes)
   at System.Data.Services.Providers.ObjectContextServiceProvider.PopulateMetadata(IDictionary`2 knownTypes, IDictionary`2 entitySets)
   at System.Data.Services.Providers.BaseServiceProvider.PopulateMetadata()
   at System.Data.Services.DataService`1.CreateProvider(Type dataServiceType, Object dataSourceInstance, DataServiceConfiguration&amp; configuration)
   at System.Data.Services.DataService`1.EnsureProviderAndConfigForRequest()
   at System.Data.Services.DataService`1.ProcessRequestForMessage(Stream messageBody)
   at SyncInvokeProcessRequestForMessage(Object , Object[] , Object[] )
   at System.ServiceModel.Dispatcher.SyncMethodInvoker.Invoke(Object instance, Object[] inputs, Object[]&amp; outputs)
   at System.ServiceModel.Dispatcher.DispatchOperationRuntime.InvokeBegin(MessageRpc&amp; rpc)
   at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage5(MessageRpc&amp; rpc)
   at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage4(MessageRpc&amp; rpc)
   at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage3(MessageRpc&amp; rpc)
   at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage2(MessageRpc&amp; rpc)
   at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage1(MessageRpc&amp; rpc)
   at System.ServiceModel.Dispatcher.MessageRpc.Process(Boolean isOperationContextSet)</ExceptionString>
</Exception>
</TraceRecord>
</DataItem>
</TraceData>
</ApplicationData>
</E2ETraceEvent>

Answer 1

我最近遇到了一个类似的问题，修复方法是将EntitySetAccessRule的名称更改为"*"，如下所示：

public static void InitializeService(DataServiceConfiguration config)
{
  config.SetEntitySetAccessRule("*", EntitySetRights.All);
  config.DataServiceBehavior.MaxProtocolVersion = DataServiceProtocolVersion.V2;
}

Answer 2

我也遇到过类似的问题，这是由于将错误的类传递给DataService造成的。您需要传递数据模型的data entities类。

public class WebDataService : DataService< DataModel.DataEntities >

Answer 3

我也遇到了同样的问题，解决方案很简单:虽然我的表名和生成的实体对象是单数"Order"，但在这个上下文中，我需要将其称为“Order”。我还在想这件事。只是EDM标准。

config.SetEntitySetAccessRule("Orders", EntitySetRights.All);

希望这能有所帮助。