using System;

using System.Collections.Generic;

using System.Text.RegularExpressions;

​

public class Program

{

    public static void Main()

    {

        // JS: s.split(/\?{0}\+/g).join('\n').replace(/\?\n/g, '+').split(/\n/)

        string s = "nika ?+ marry = love+sandra ?+ alex = love";

        string[] result = Regex.Split(s, "\\?{0}\\+", RegexOptions.Multiline);                  

        s = String.Join("\n", result);      

        Regex rgx = new Regex("\\?\\n");

        s = rgx.Replace(s, "+");

        result = Regex.Split(s, "\\n", RegexOptions.Multiline);                         

        foreach (string match in result)

        {

            Console.WriteLine("'{0}'", match);

        }   

    }

}