XML : Replace text with one or more \n using regex? in c#.net

Kindly check below mention link for example

https://social.msdn.microsoft.com/Forums/en-US/11afd597-1367-4b17-929e-91487ffb7c95/replace-text-with-one-or-more-n-using-regex-in-cnet?forum=csharpgeneral