Как получить последнюю строку/абзац выделения в RichTextBox?

Наконец я нашел этот способ получить последнюю строку в выборе. Кажется, работает.

// In my case "this" is the RichTextBox itself, because I work in a derived class from RichTextBox
Paragraph lastLineInSelection = this.Selection.End.Paragraph;
if (this.Selection.End.IsAtLineStartPosition)
{
    Block previousBlock = this.Selection.End.Paragraph.PreviousBlock;
    while (previousBlock is Paragraph == false && previousBlock != null)
        previousBlock = previousBlock.PreviousBlock;

    if (previousBlock != null)
        lastLineInSelection = (previousBlock as Paragraph);
}