My C# ObservableDictionary

namespace DynamicSpikes
{
    public class ObservableDictionary<String, Object> : Dictionary<string, object>, INotifyPropertyChanged, INotifyCollectionChanged
    {

        public event PropertyChangedEventHandler PropertyChanged = delegate { };
        public event NotifyCollectionChangedEventHandler CollectionChanged = delegate { };

        private void OnCollectionChanged(object sender, NotifyCollectionChangedAction action, object value)
        {
            if (CollectionChanged != null)
            {
                CollectionChanged(sender, new NotifyCollectionChangedEventArgs(action, value));
            }
        }

        private void OnPropertyChanged(object sender, string propertyName)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
            }
        }

        public new void Add(string key, object value)
        {
            base.Add(key, value);
            OnCollectionChanged(this, NotifyCollectionChangedAction.Add, new KeyValuePair<string, object>(key, value));

            //OnPropertyChanged(this, "Values");
            //OnPropertyChanged(this, "Keys");
            //OnPropertyChanged(this, "Count");
        }

        public new bool Remove(string key)
        {
            var kvp = base[key];
            var result = base.Remove(key);
            if (result)
            {
                OnCollectionChanged(this, NotifyCollectionChangedAction.Remove, kvp);

                //OnPropertyChanged(this, "Values");
                //OnPropertyChanged(this, "Keys");
                //OnPropertyChanged(this, "Count");
            }
            return result;
        }

        public new object this[string key]
        {
            get
            {
                return base[key];
            }
            set
            {
                base[key] = value;
                PropertyChanged(this, new PropertyChangedEventArgs(key));
            }
        }
    }