Entity Framework - Detached Update issue

Question

Ok, I am attempting to use this custom extension to perform an entity update. Right now it should update all properties and then all of its related ends (references). The problem is even though the entity with changes does have a related end with an entity key that is valid and correct (verified in the debugger its there). When the RelationshipManager gets it they key is null.. Anyone see anything wrong with this code?

public static void ApplyChanges(this ObjectContext context, EntityObject entityWithChanges)
 {
  if (entityWithChanges.EntityState == EntityState.Detached)
  {
   object entityCurrentlyInDB = null;

   if (context.TryGetObjectByKey(entityWithChanges.EntityKey, out entityCurrentlyInDB))
   {
    context.ApplyPropertyChanges(entityWithChanges.EntityKey.EntitySetName, entityWithChanges);

    foreach (var relatedEnd in ((IEntityWithRelationships)entityCurrentlyInDB).RelationshipManager.GetAllRelatedEnds())
    {
     var oldRef = relatedEnd as EntityReference;

     if (oldRef != null)
     {
      var newRef =
       ((IEntityWithRelationships)entityWithChanges).RelationshipManager
       .GetRelatedEnd(oldRef.RelationshipName, oldRef.TargetRoleName) as EntityReference;
      oldRef.EntityKey = newRef.EntityKey;
     }
    }
   }
   else
   {
    throw new ObjectNotFoundException();
   }

  }
 }

This is just a modified version of what I found Here

Appreciate the help.

UPDATE: This is the Update Method

public static void UpdateTemplate(Template template)
 {
  using (TheEntities context = new TheEntities())
  {
   context.ApplyChanges(template);
   try
   {
    context.SaveChanges();
   }
   catch (OptimisticConcurrencyException)
   {
    context.Refresh(RefreshMode.ClientWins, template);
    context.SaveChanges();
   }

   context.RemoveTracking(template);
  }
 }

This is the unit test:

[TestMethod]
 public void CanUpdateATemplate()
 {
  Template template = new Template();
  template.Name = "Test";
  template.Description = "Test";

  TemplateType type = TemplateManager.FindTemplateTypeByName("Test");

  if (type == null)
  {
   type = new TemplateType();
   type.Name = "Test";
  }

  template.TemplateType = type;

  TemplateManager.AddTemplate(template);

  template = TemplateManager.FindTemplateByID(template.TemplateID);

  Assert.IsNotNull(template);

  type = TemplateManager.FindTemplateTypeByName("Round");

  if (type == null)
  {
   type = new TemplateType();
   type.Name = "Round";
  }

  template.TemplateType = type;

  TemplateManager.UpdateTemplate(template);

  template = TemplateManager.FindTemplateByID(template.TemplateID);

  Assert.IsNotNull(template);
  Assert.IsTrue(template.TemplateType.Name == "Round");

  TemplateManager.DeleteTemplate(template);

  template = TemplateManager.FindTemplateByID(template.TemplateID);

  Assert.IsNull(template);
 }

Answer 1

This is simply not possible due to the way Detach works in EF.

I found that if I added key information myself I could get the generic call to work and even save it.

The problem is that the moment you go to return an entity after calling Detach on it you lose all relationship data. Ive found some write ups on writing graph managers for each entity but I find that a waste seeing as EF should do this stuff (supposedly it will in v2).

EF simply is not ready for N-Tier deployments.