You can add double quotes or other special characters by “escaping” them. For example:
string escapedStr = "\"First line\nSecond line\"";
See
this site[
^] for a list of available escape characters.
As Mattias said you can simply prepend “@” to your string, however you need to be aware that it has some other effects; it causes escape characters to be treated as literals. See
this article[
^] for more details.