WCF 数据服务请求错误

Question

I used the following GettingStarted to create my first WCF Data Service with a Connection to a Database. https://msdn.microsoft.com/en-us/data/gg192995.aspx

I made it until step 13, but i don't get any xml feed. Instead i get the following message (unfortunately in german):

Auf dem Server ist bei der Verarbeitung der Anforderung ein Fehler aufgetreten. Die Ausnahmemeldung lautet 'Ein Ausdruck vom Typ "System.Data.Entity.Core.Objects.ObjectContext" kann nicht für den Rückgabetyp "System.Data.Objects.ObjectContext" verwendet werden.'. Ausführlichere Informationen finden Sie in den Serverprotokollen. Die Ausnahmestapelüberwachung lautet folgendermaßen:

bei System.Linq.Expressions.Expression.ValidateLambdaArgs(Type delegateType, Expression& body, ReadOnlyCollection 1 parameters) bei System.Linq.Expressions.Expression.Lambda[TDelegate](Expression body, String name, Boolean tailCall, IEnumerable 1 parameters) bei System.Data.Services.Providers.DbContextHelper.CreateDbContextAccessor(Type type) bei System.Data.Services.Providers.DbContextHelper.GetDbContextAccessor(Type type) bei System.Data.Services.DataService 1.CreateMetadataAndQueryProviders(IDataServiceMetadataProvider& metadataProviderInstance, IDataServiceQueryProvider& queryProviderInstance, Object& dataSourceInstance, Boolean& isInternallyCreatedProvider) bei System.Data.Services.DataService 1.CreateProvider() bei System.Data.Services.DataService 1.HandleRequest() bei System.Data.Services.DataService 1.ProcessRequestForMessage(Stream messageBody) bei SyncInvokeProcessRequestForMessage(Object , Object[] , Object[] ) bei System.ServiceModel.Dispatcher.SyncMethodInvoker.Invoke(Obje ct instance, Object[] inputs, Object[]& outputs) bei System.ServiceModel.Dispatcher.DispatchOperationRuntime.InvokeBegin(MessageRpc& rpc) bei System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage5(MessageRpc& rpc) bei System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage41(MessageRpc& rpc) bei System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage4(MessageRpc& rpc) bei System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage31(MessageRpc& rpc) bei System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage3(MessageRpc& rpc) bei System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage2(MessageRpc& rpc) bei System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage11(MessageRpc& rpc) bei System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage1(MessageRpc& rpc) bei System.ServiceModel.Dispatcher.MessageRpc.Process(Boolean isOperationContextSet)

Maybe it don't work because of newer versions from SQL Server, IIS or Visual Studio?

Maybe some namespace problems?

The error message says that System.Data.Entity.Core.Objects.ObjectContext cannot be converted into System.Data.Objects.ObjectContext.

Here is the code from the WcfDataService1.svc.cs file

//------------------------------------------------------------------------------
// <copyright file="WebDataService.svc.cs" company="Microsoft">
//     Copyright (c) Microsoft Corporation.  All rights reserved.
// </copyright>
//------------------------------------------------------------------------------
using System;
using System.Collections.Generic;
using System.Data.Services;
using System.Data.Services.Common;
using System.Linq;
using System.ServiceModel.Web;
using System.Web;
using System.ServiceModel;

namespace RestWcfService
{
    [ServiceBehavior(IncludeExceptionDetailInFaults = true)]
    public class WcfDataService1 : DataService<AdventureWorksLTEntities>
    {
        // This method is called only once to initialize service-wide policies.
        public static void InitializeService(DataServiceConfiguration config)
        {
            // TODO: set rules to indicate which entity sets and service operations are visible, updatable, etc.
            // Examples:
            config.UseVerboseErrors = true;
            config.SetEntitySetAccessRule("MyEntityset", EntitySetRights.AllRead);
            config.SetServiceOperationAccessRule("MyServiceOperation", ServiceOperationRights.All);
            config.DataServiceBehavior.MaxProtocolVersion = DataServiceProtocolVersion.V3;
        }
    }
}

Answer 1

That's a common issue when upgrading from an older version of Entity Framework to version 6. System.Data.Objects.ObjectContext is not a part of EF 6. Best thing to do is remove the packages and reinstall.

Replace System.Data.Objects.ObjectContext => System.Data.Entity.Core.Objects.ObjectContext

https://msdn.microsoft.com/en-us/data/upgradeef6.aspx