第一种:
<TextBlock>
This is line 1.<LineBreak/>
This is line 2.
</TextBlock>
第二种
<TextBlock xml:space="preserve">This is line 1.
This is an indented line 2.</TextBlock>
第二种加了xml:space="preserve",可以直接在文本上按space,tab键,不用标记,比较方便