public TokenCollection( params string[] tokens )
{
if( CollectionChanged != null )
CollectionChanged( this, new NotifyCollectionChangedEventArgs( NotifyCollectionChangedAction.Reset ) );
_token = new List<IToken>( tokens.Select( t => new Token( t ) ) );
if( CollectionChanged != null )
CollectionChanged( this, new NotifyCollectionChangedEventArgs( NotifyCollectionChangedAction.Add, _token ) );
}