ADO.NET实体框架和WCF服务

Question

I have a simple ADO.NET Entity Framework 4.0 model (edmx) which defines database tables with foreign key relationships.

How can I send these entities down to a Windows Phone 7 client? I have created a WCF Service (using WShttpbinding),with the method...

public List<LocationCity> ListCities()
{    
   var dc = ObjectFactory.GetInstance<TestEntities>();
   var locs = dc.LocationCities.Take(10).ToList();
   return locs;
}

I also created a simple Console application to consume this service, but it doesn't work... In the trace I see the exception

Maximum number of items that can be serialized or deserialized in an object graph is '65536'

at System.ServiceModel.Dispatcher.DataContractSerializerOperationFormatter.SerializeParameterPart

I then changed MaxItemsInObjectGraph to a massive number, just to see what would happen and I get a stack overflow exception then. So it looks to me that the dataContractSerializer is navigating cyclic properties on the object graph and getting into a recursive loop.

All I want to do is send 10 LocationCity entities down to the client (whether Windows Phone or Console).

I suppose I could create separate DataContract POCO entities, and populate them from the select on the context... however, I don't really want to have to duplicate classes for no good reason. I figure I must be doing something wrong.

I would really appreciate some help!

Answer 1

The trick to deal with circular references is to use [DataContract(IsReference=true)]. IsReference property is available since .NET 3.5 SP1 so it should not be problem for you.

Best regards, Ladislav

Answer 2

I had set "LazyLoadingEnabled" to true within entities designer. Just had to set it to false and everything is fine!