Entity Framework - Disconnexted Behavior in nTier - entity-framework-4

Question

I am new to EF but I will try my best to describe the scenario. I have 3 tables in My DB namely RecommendationTopic, Recommendation and Question. Each RecommendationTopic can have multiple Recommendations and each Recommendation may have multiple questions. Assume that I already have predefined questions in my Question table.
I have one service that returns me list of questions like below:
public List<Question> FetchQuestions(int categoryID)
{
using (Entities context = new Entities())
{
questions = context.Questions.Where(i => i.ID >= 0).ToList();
}
}
I have another service which is used to create RecommendationTopic and Recommendation whose code is something like below:
public void ManageRecommendation(RecommendationTopic recommendationTopic)
{
using (Entities context = new Entities())
{
context.AddObject("RecommendationTopics", recommendationTopic);
context.SaveChanges();
}
}
My client code looks like below:
List<Question> questions;
using (QuestionServiceClient client = new QuestionServiceClient())
{
questions = client.FetchQuestions();
}
using (RecommendationServiceClient client = new RecommendationServiceClient())
{
RecommendationTopic rTopic = new RecommendationTopic();
rTopic.CategoryID = 3;
rTopic.Name = "Topic From Client";
Recommendation rCom = new Recommendation();
rCom.Text = "Dont!";
rCom.RecommendationTopic = rTopic;
rCom.ConditionText = "Some condition";
rCom.Questions.Add(questions[0]);
rCom.Questions.Add(questions[1]);
client.ManageRecommendation(rTopic);
}
Since the client makes 2 separate service calls, the context would be different for both the calls. When I try to run this and check the EF profiler, it not only generates query to insert into RecommendationTopic and Recommendation but also Question table!
I am sure this is caused due to different context for both the calls as when I execute a similar code within a single context, it works as it's supposed to work.
Question is, how do I make it work in a disconnected scenario?
My client could be Silverlight client where I need to fill a Question drop down with a separate call and save Recommendation topic in a separate call. For this reason I am using self tracking entities as well.
Any input appreciated!
-Vinod

Answer 1

If you are using STEs (self tracking entities) your ManageRecommendation should look like:
public void ManageRecommendation(RecommendationTopic recommendationTopic)
{
using (Entities context = new Entities())
{
context.RecommendationTopics.ApplyChanges(recommendationTopic);
context.SaveChanges();
}
}
Calling AddObject skips self tracking behavior of your entity. If you are not using STEs you must iterate through all questions and change their state to Unchanged:
public void ManageRecommendation(RecommendationTopic recommendationTopic)
{
using (Entities context = new Entities())
{
context.RecommendationTopics.AddObject(recommendationTopic);
foreach (var question in recommendationTopic.Questions)
{
context.ObjectStateManager.ChangeObjectState(recommendationTopic, EntityState.Unchanged);
}
context.SaveChanges();
}
}