Entity Framework ObjectSet detach method functionality

Question

Well, first of all I'll explain the whole situation. I have simple POCO domain model which I'm persisting with EF 4.0. For the first time I used only navigation properties and no FK properties. But later due to some binding purposes I decided to add FK properties to my model (Company_ID in the code below). Here are two classes from that model:

public class Company:EntityObject<Int32>, {       
        public virtual string Name { get; set; }        
        public virtual string Phone { get; set; }
        public virtual string Fax { get; set; }
        public virtual IList<Customer> Customers { get; set; }        
    }

public class Customer:EntityObject<Int32> {        
        public virtual string FirstName { get; set; }
        public virtual string LastName { get; set; }            
        public virtual Company Company { get; set; }
        public virtual int Company_ID { get; set; }        
    }

I simplified this model a little bit just to highlight the main issue. After adding FK properties I regenerated the EDMX with FK inclusion. So now some of my test code doesn't work anymore. The problem is with detach method of ObjectSet (Repository Detach is a wrapper around it). Here is the test code:

using (IEntityModelContext context = new EFDataContext()) {
                var compFact = context.GetFactory<Company>();
                var custFact = context.GetFactory<Customer>();                
                Company comp = compFact.CreateObject();                
                comp.Fax = "111111";
                comp.Name = "Testcomp";
                comp.Phone = "222222";                
                context.CompanyRepository.Add(comp);                
                context.SaveChanges();                
                Customer cust = custFact.CreateObject();                
                cust.FirstName = "John";              
                cust.LastName = "Smith";                                
                comp.Customers.Add(cust);               
                context.SaveChanges();                
                context.CompanyRepository.Detach(comp);                
                Company newComp = context.CompanyRepository.Load(com => com.Name == "Testcomp");
                Assert.IsNotNull(newComp);
                Assert.IsFalse(newComp.IsTransient);
                Assert.AreEqual(comp.Fax, newComp.Fax);
                Assert.AreEqual(industryList.Values[0], newComp.Industry);
                Assert.AreEqual(comp.Name, newComp.Name);
                Assert.AreEqual(comp.Phone, newComp.Phone);
                Assert.AreEqual(sizeList.Values[0], newComp.Size);
                Assert.AreEqual(1, newComp.Customers.Count);

The problem rises when newComp object is loaded: Customers property is empty, moreover it's null (I checked the DB - Customer was successfully saved). So the last assertion fails. This code worked quite well until I added FK property. So is there any explanation of this behavior?

Answer 1

Assuming it was successfully saved to the db (so the customer/company relationship exists in db)

The problem lies in the fact that you did not load the reference to Customers. So either:

A) Include Customers when you retrieve company from the context, or

B) Lazy Load it before you check the reference.