带格式分离两个RichEditControl的文本

using( RichEditControl selector = new RichEditControl() {
RtfText = richTextFromHtml 
} ) {
DocumentRange rangeBlockOne = selector.Document.CreateRange( 0, 19 );
DocumentRange rangeBlockTwo = selector.Document.CreateRange( 19, 49 );
richTextBlockOne = selector.Document.GetRtfText( rangeBlockOne );
richTextBlockTwo = selector.Document.GetRtfText( rangeBlockTwo );
}