using System;

using System.Text.RegularExpressions;                   

public class Program

{

    public static void Main()

    {

        var regex = @"^((?!\s{2,}).)*$";

        var temp = Regex.IsMatch("TES\r\nT",regex);

        if(temp)

        {

            Console.Write("match");

        }

        else Console.Write(" not match");

    }

 }

​