List<Controls> list = new List<Controls>

myObject.myList.Add(new Control());

myList.AddingEvent += HandleAddingEvent

using System;
using System.Collections.Generic;

namespace test {
    class Program {

        class MyList<T> : List<T> {

            public event EventHandler OnAdd;

            public void Add(T item) {
                if (null != OnAdd) {
                    OnAdd(this, null);
                }
                base.Add(item);
            }

        }

        static void Main(string[] args) {
            MyList<int> l = new MyList<int>();
            l.OnAdd += new EventHandler(l_OnAdd);
            l.Add(1);
        }

        static void l_OnAdd(object sender, EventArgs e) {
            Console.WriteLine("Element added...");
        }
    }
}

ObservableCollection<int> myList = new ObservableCollection<int>();

myList.CollectionChanged += new System.Collections.Specialized.NotifyCollectionChangedEventHandler(
    delegate(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
    {
        if (e.Action == System.Collections.Specialized.NotifyCollectionChangedAction.Add)
        {
            MessageBox.Show("Added value");
        }
    }
);

myList.Add(1);