notify the derived class when an item added , replaced or Removed from the Collection

Create Custom Event Class: derived from EventArgs class

 public class CustomEvent : EventArgs
    {
        public CustomEvent(string message)
        {
            this.Message = message;
        }
        public string Message
        {
            get;
            set;
        }
    }

declare a delegate out side the Class:

public delegate void CustomEventHandler(object sender,CustomEvent args);

Create the Class Branch Contains Inner class BranchNameCollection holds the item Collection  

public class Branch
    {
        BranchNameCollection _branchNames;

        #region --Event Raised when item is Removed--

        //public event EventHandler itemRemoved;
        public event CustomEventHandler itemRemoved;
        public event CustomEventHandler itemAdded;
        public event CustomEventHandler itemReplaced;
        #endregion

        public Branch()
        {
            this._branchNames = new BranchNameCollection(this);
        }

        #region Property

        public Collection BranchNames
        {
            get { return _branchNames; }
        }

        #endregion

        //---called from within the BranchNamesCollection class when item Removed---
        protected virtual void RaiseItemRemovedEvent(CustomEvent e)
        {
            if (itemRemoved != null)
                itemRemoved(this, e);
        }

        //---called from within the Branchnamecollection class when item to be added----
        protected virtual void RaisedAddItemEvent(CustomEvent e)
        {
            if (itemAdded != null)
                itemAdded(this, e);
        }
        protected virtual void RaisedReplaceItemEvent(CustomEvent e)
        {
            if (itemReplaced != null)
                itemReplaced(this, e);
        }
        public string Message
        {
            get; set;
        }
        private class BranchNameCollection : Collection
        {
            Branch _b;
            public BranchNameCollection(Branch b)
            {
                this._b = b;
            }
            //---fired when an item is removed---
            protected override void RemoveItem(int index)
            {
                _b.RaiseItemRemovedEvent(new CustomEvent(_b.BranchNames[index].ToString()));
                base.RemoveItem(index);
            }
            //---fired when an item Added---
            protected override void InsertItem(int index, string item)
            {
                base.InsertItem(index, item);
                _b.RaisedAddItemEvent(new CustomEvent(_b.BranchNames[index].ToString()));
               
            }
            //---fired when an item Replaced---
            protected override void SetItem(int index, string item)
            {
                base.SetItem(index, item);
                _b.RaisedReplaceItemEvent(new CustomEvent(_b.BranchNames[index].ToString()));
            }
        }
    }


calling the Void  main()
{
         //creating the object
         Branch b = new Branch();
        //assign Events and handle the Events
            b.itemRemoved += new CustomEventHandler(b_itemRemoved);
            b.itemAdded+= new CustomEventHandler(b_itemAdded);
            b.itemReplaced+=new CustomEventHandler(b_itemReplaced);
            b.BranchNames.Add("Mumbai");
            b.BranchNames.Add("Kolkata");
            b.BranchNames.Add("Bangalore");
            b.BranchNames.Add("Delhi");
           
            //Remove the item from collection
            b.BranchNames.Remove("Kolkata");

}
//calling Appropriate function

        static void  b_itemRemoved (object sender, CustomEvent args)
        {
            Console.WriteLine("ItemRemoved "+ " : " + args.Message);
        }

        static void b_itemAdded(object sender, CustomEvent args)
        {
            Console.WriteLine("ItemAdded " + " : " + args.Message);
        }
        static void b_itemReplaced(object sender, CustomEvent args)
        {
            Console.WriteLine("ItemReplaced " + " : " + args.Message);
        }
//