What do you mean by "break a string"?
And where are newlines significant?
Strings don't have "breaks" and a newline is just a character or character sequence as far as a string is concerned. It's only when a string is output to a browser, display, or printer that line breaks become relevant - and then it depends on the environment what you do to perform a newline.
For example, outputting to a console:
Console.WriteLine("Cana");
Console.WriteLine("nyon");
and
Console.WriteLine("Cana\nnyon");
are equivelant, and put in two newlines.
But for a browser, you need HTML:
Response.Write("Cana<br />nyon<br />");
Is needed.
For printing, or output to displays via Paint events, it gets even more complex.
Basically, a string isn't an "output-able" object, and it has no concept of a line break - so there is no "one size fits all" answer we can give.