How do I get the old values of an entity?

How do I get the old values of an entity?

follows the example..

public void Update(User user)
    ValidateEntity(user, OperationType.Update);

    oldUser = (how do I get the old values ​​(database) of the entity User?)

    Set.Attach(user);
    Context.ObjectStateManager.ChangeObjectState(user, EntityState.Modified);
    Context.SaveChanges();

    OnUpdated(user, oldUser);
}

Try this:

public void Update(User user)
    ValidateEntity(user, OperationType.Update);

    var oldUser = Set.Single(u => u.Id == user.Id);
    Context.Detach(oldUser);

    Set.Attach(user);
    Context.ObjectStateManager.ChangeObjectState(user, EntityState.Modified);
    Context.SaveChanges();

    OnUpdated(user, oldUser);
}

Or this:

public void Update(User user) 
{
    ValidateEntity(user, OperationType.Update);

    var oldUser = Set.Single(u => u.Id == user.Id);
    Set.ApplyCurrentValues(user);
    Context.SaveChanges(SaveOptions.DetectChangesBeforeSave);

    OnUpdated(user, Context.ObjectStateManager.GetOjectStateEntry(user).OriginalValues);

    Context.AcceptAllChanges(); 
}