events - collection oninsert onremove at design time -

hi trying usercontrol refresh (invalidate) self when in design mode collection editor open. have success when adding tab collection, not when removing tab collection. ideas?

public class tabcollection : system.collections.collectionbase {     //declares     internal tabcontrol owner;     //list     public tabcollection() : base()      {     }     public tabcollection(tabstripcontrol tabs_owner) : base()     {         owner = tabs_owner;     }     //returns tab properties collection list     public tab this[int index]     {                 {             return (tab)(list[index]);         }         set         {             list[index] = value;         }     }     protected override void oninsert(int index, object value)     {         if (owner != null)         {             //refresh             owner.invalidate(); //<<<<---this works here         }     }     protected override void onremove(int index, object value)     {         if (owner != null)         {             //refresh             owner.invalidate(); //<<<<---this not work here         }     } }