using System;

​

public class Program

{

    public static void Main()

    {

        test("simple\tstring   ");

        test("just line\n  feed");

        test("just carriage\n  return");

        test(@"

here string

contains Windows newlines");

        void test(string s)

        {

            bool result = ContainsNewlineCharacter(s);

            Console.WriteLine($"Input: '{s}'\r\nContains Newlines? {result}");

            Console.WriteLine();

        }

​

        bool ContainsNewlineCharacter(string s)

        {

            return s.IndexOfAny(new[] { '\r', '\n' }) >= 0;

        }

    }

}