EF Code First + remove orphans which marked as Modified (IsDeleted = 1) - ef-code-first

Question

I have the next problem. My code context + model:
public class MediaPlanContext : DbContext
{
public MediaPlanContext() : base(lazyLoading:false) {}
public DbSet<MediaPlan> MediaPlan { get; set; }
public DbSet<MovieType> MovieType { get; set; }
public DbSet<MediaPlanItem> MediaPlanItems { get; set; }
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
base.OnModelCreating(modelBuilder);
modelBuilder
.Entity<MediaPlanItem>()
.HasKey(mpi => new {mpi.Id, mpi.MediaPlanId});
modelBuilder
.Entity<MediaPlanItem>()
.Property(mpi => mpi.Id)
.HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);
modelBuilder
.Entity<MediaPlan>()
.HasMany(mp => mp.MediaPlanItems)
.WithRequired()
.HasForeignKey(mpi => mpi.MediaPlanId)
.WillCascadeOnDelete();
}
}
public class MediaPlan : IBaseObject
{
public virtual ICollection<MediaPlanItem> MediaPlanItems { get; set; }
}
public class MediaPlanItem : IBaseObject
{
public int MediaPlanId {get;set;}
public MediaPlan MediaPlan {get;set;}
}
public interface IBaseObject
{
public int Id {get;}
public DateTime DateCreated {get;}
public DateTime DateModified {get;set;}
}
Also I use repository to handle with my objects (IBaseObject-s) with root-object MediaPlan.
When object in my DB will become deleted I mark entity (record) as IsDeleted = 1 and I have some logic in my repository class to handle regular delete as update, change EntityState to Modified instead of Deleted.
Problem with the next code:
var rep = new MediaPlanRepository(new MediaPlanContext());
var withItems = rep.GetWithMediaPlanItems();
var m1 = withItems.First();
var mpi1 = m1.MediaPlanItems.First();
m1.MediaPlanItems.Remove(mpi1); // 6 items before remove
// 5 items after remove
rep.SaveChanges();
// 6 items after save changes :(
Question: Can I handle the moment after saveChanges occurs and detach my IsDeleted = 1 entity? Is is resolve my problem?
Remark: Related entities loaded to root object as projection and as Julie says in paragraph 'Scenario When This May Not Work As Expected' can produce problems with entities that is already tracked by context.

Answer 1

Code:
public override int SaveChanges()
{
var result = base.SaveChanges();
// AfterSave code
var isDeletedEntities = EfContext.ChangeTracker
.Entries()
.Select(dbE => new {
DBEntity = dbE,
BaseObject = (dbE.Entity as IBaseObject)})
.Where(dbe => dbe.BaseObject.IsDeleted);
foreach (var isDeletedEntity in isDeletedEntities)
{
isDeletedEntity.DBEntity.State = EntityState.Detached;
}
}