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Today I wanted to created simple out of a box Odata service using WCF Dataservice. My entry page was explaining how to get error details. essentially you need just two steps:

First set config.UseVerboseErrors = true in your service cs file

   1:   // This method is called only once to initialize service-wide policies.
   2:          public static void InitializeService(DataServiceConfiguration config)
   3:          {
   4:              // TODO: set rules to indicate which entity sets and service operations are visible, updatable, etc.
   5:              // Examples:
   6:              config.UseVerboseErrors = true;
   7:              config.SetEntitySetAccessRule("ExampleClass", EntitySetRights.AllRead);
   8:              // config.SetServiceOperationAccessRule("MyServiceOperation", ServiceOperationRights.All);
   9:              config.DataServiceBehavior.MaxProtocolVersion = DataServiceProtocolVersion.V2;
  10:          }

Second: attribute your class with ServiceBehavior(IncludeExceptionDetailInFaults = true)] 

[System.ServiceModel.ServiceBehavior(IncludeExceptionDetailInFaults = true)]
  public class ExampleService : DataService<  ExampleContext >

Ok once this has been changed I got nice error:

The server encountered an error processing the request. The exception message is ‘On data context type ‘ExampleContext’, there is a top IQueryable property ‘Examples’ whose element type is not an entity type. Make sure that the IQueryable property is of entity type or specify the IgnoreProperties attribute on the data context type to ignore this property.’. See server logs for more details. The exception stack trace is:

at System.Data.Services.Providers.ReflectionServiceProvider.PopulateMetadata(IDictionary`2 knownTypes, IDictionary`2 childTypes, IDictionary`2 entitySets) at System.Data.Services.Providers.BaseServiceProvider.PopulateMetadata() at System.Data.Services.DataService`1.CreateProvider() at System.Data.Services.DataService`1.HandleRequest() 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[]& outputs) at System.ServiceModel.Dispatcher.DispatchOperationRuntime.InvokeBegin(MessageRpc& rpc) at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage5(MessageRpc& rpc) at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage41(MessageRpc& rpc) at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage4(MessageRpc& rpc) at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage31(MessageRpc& rpc) at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage3(MessageRpc& rpc) at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage2(MessageRpc& rpc) at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage11(MessageRpc& rpc) at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage1(MessageRpc& rpc) at System.ServiceModel.Dispatcher.MessageRpc.Process(Boolean isOperationContextSet)

 

After searching a little bit I found that you need attribute your entity with primary key attribute DataServiceKey

 

[DataServiceKey("Id")]
    public class ExampleClass
    {

         public string Name { get; set; }
         public string Id { get; set; }
    }