/// <summary>
        /// Releases unmanaged resources used by ContextPopup.
        /// </summary>
        /// <param name="isDisposing">Flag indicating whether process of disposing lasts or not.</param>
        protected virtual void Dispose(bool isDisposing)
        {
            if (_isDisposed)
            {
                return;
            }

            if (isDisposing)
            {
                if (_popup != null)
                {
                    _popup.Unrealize();
                    _popup = null;
                }
            }

            _isDisposed = true;
        }