Entity Framework 6 - GetObjectStateEntries expected modified entities have state "Unchanged" - entity-framework

Question

Issue
When I create my Account-class as example A, the object appears with state "EntityState.Modified" in my SaveChanges()-method as expected.
When I use example B, the object appears as "EntityState.Unchanged" and does no apear in the result of the GetObjectStateEntries(EntityState.Added | EntityState.Modified) call.
Can anyone explain to me, why the model object appears unchanged in example B while everything works in example A?
Thankyou
Classes
I update 'Created' and 'LastUpdated' using this method in my Context object:
public class CrmContext : DbContext
{
public override int SaveChanges()
{
DateTime now = DateTime.Now;
foreach (ObjectStateEntry entry in (this as IObjectContextAdapter).ObjectContext.ObjectStateManager.GetObjectStateEntries(EntityState.Added | EntityState.Modified))
{
if (!entry.IsRelationship)
{
var account = entry.Entity as Account;
if (account != null)
{
account.LastUpdated = now;
if (entry.State == EntityState.Added)
{
account.Created = now;
}
}
}
}
return base.SaveChanges();
}
}
Model example A (WORKING):
public class Account
{
[Key]
public int AccountId { get; set; }
public string Name { get; set; }
[Timestamp]
public Byte[] TimeStamp { get; set; }
public DateTime Created { get; set; }
public DateTime LastUpdated { get; set; }
}
Model example B (NOT WORKING):
public class Account : BaseObject
{
[Key]
public int AccountId { get; set; }
public string Name { get; set; }
}
public class BaseObject
{
[Timestamp]
public Byte[] TimeStamp { get; set; }
public DateTime Created { get; set; }
public DateTime LastUpdated { get; set; }
}
UPDATE:
The problem does not seem to have anything to do with whether the model class inherits from a base class or not as I cannot reproduce a working example without using the suggested DetectChanges() call.

Answer 1

You should call change detection manually at the beginning of the overridden SaveChanges method:
public override int SaveChanges()
{
this.ChangeTracker.DetectChanges();
//...
}
I have no explanation why the entity state might be different for model A and model B. But the missing call to DetectChanges generally can be a reason why an entity is in state Unchanged (temporarily) although it has been modified. For example if you have POCO entities (not change tracking proxies), just load an entity, change a property and then call your overridden SaveChanges the state will be Unchanged until base.SaveChanges is called which would update the state to Modified and save the change to the database. But your code that sets the LastUpdated property would have been skipped and LastUpdated had the old value in the database.