private void RemoveText(int position, int length)
        {
            if (length == 0)
            {
                return;
            }

            MaskProvider.RemoveAt(position, position + length - 1);
        }
        private bool RemoveSelectedText()
        {
            int length = SelectionLength;

            if (length == 0)
            {
                return(false);
            }

            int position = SelectionStart;

            return(MaskProvider.RemoveAt(position, position + length - 1));
        }