Incomplete ObservableCollection with Rx

ObservableCollection

using System;
using System.Collections.Generic;
using System.Reactive.Disposables;

namespace ReactiveExtensions.Rx
{
    public class ObservableCollection<T> : IList<T>, System.IObservable<T>
    {
        private IList<T> list;
        private IList<IObserver<T>> observers;

        public ObservableCollection ()
        {
            this.list = new List<T>();
            this.observers = new List<IObserver<T>>();
        }

        #region IObservable implementation

        public IDisposable Subscribe (IObserver<T> observer)
        {
            this.observers.Add (observer);
            return Disposable.Create(() => this.observers.Remove(observer));
        }

        private void NotifyNext(T item)
        {
            foreach (var observer in observers) {
                observer.OnNext(item);
            }
        }

        #endregion

        #region IList implementation

        public int IndexOf (T item)
        {
            return this.list.IndexOf(item);
        }

        public void Insert (int index, T item)
        {
            this.list.Insert(index, item);
            this.NotifyNext(item);
        }

        public void RemoveAt (int index)
        {
            this.list.RemoveAt(0);
        }

        public T this [int index] {
            get {
                return this.list[index];
            }
            set {
                this.list[index] = value;
            }
        }

        #endregion

        #region ICollection implementation

        public void Add (T item)
        {
            this.list.Add (item);
            this.NotifyNext(item);
        }

        public void Clear ()
        {
            this.list.Clear();
        }

        public bool Contains (T item)
        {
            return this.list.Contains(item);
        }

        public void CopyTo (T[] array, int arrayIndex)
        {
            this.list.CopyTo(array, arrayIndex);
        }

        public bool Remove (T item)
        {
            return this.list.Remove(item);
        }

        public int Count
        {
            get { return this.list.Count; }
        }

        public Boolean IsReadOnly
        {
            get { return this.list.IsReadOnly; }
        }

        #endregion

        #region IEnumerable implementation

        public IEnumerator<T> GetEnumerator ()
        {
            return this.list.GetEnumerator();
        }

        #endregion

        #region IEnumerable implementation

        System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator ()
        {
            return this.list.GetEnumerator();
        }

        #endregion
    }
}