using System;

using System.Text.RegularExpressions;

public class Program

{

    public static void Main()

    {

        var badString1 = "123456789asdf"  + (char)0x0a;

        var badString2 = "123456789asdf" +  (char)0x0d+ (char)0x0a;

        //Console.WriteLine(badString1);

        //Console.WriteLine(badString2);

        //Console.WriteLine(Regex.IsMatch(badString1, @"^[0-9a-zA-Z]*$")+ " " + Regex.IsMatch(badString1, @"^[0-9a-zA-Z]+$") + " " + Regex.IsMatch(badString1, @"^[0-9a-zA-Z]{1,17}$"));

        //Console.WriteLine(Regex.IsMatch(badString2, @"^[0-9a-zA-Z]*$", RegexOptions.Singleline)+ " " + Regex.IsMatch(badString2, @"^[0-9a-zA-Z]+$") + " " + Regex.IsMatch(badString2, @"^[0-9a-zA-Z]{1,17}$"));

        //Console.WriteLine(Regex.IsMatch(badString1, @"^[0-9a-zA-Z][^\n]*$"));

        //Console.WriteLine(Regex.IsMatch(badString2, @"^[0-9a-zA-Z][^\r]*$"));

        //Console.WriteLine(Regex.IsMatch(badString1, @"^[^\\n]*$"));

        //Console.WriteLine(Regex.IsMatch(badString2, @"^[^\n]*$"));

        Console.WriteLine(Regex.IsMatch(badString1, "^[0-9a-zA-Z]*(?<!\n)$"));

        Console.WriteLine();    

​

​

        string removableChars = "" + (char)0x0a + (char)0x0d;

        //Console.WriteLine(removableChars);

        var pattern = "[" + removableChars + "]";

​

        var fixedString1 = Regex.Replace(badString1, pattern, "");

        //Console.WriteLine(fixedString1);

        var fixedString2 = Regex.Replace(badString2, pattern, "");

        //Console.WriteLine(fixedString2);

        //Console.WriteLine(Regex.IsMatch(fixedString1, @"^[0-9a-zA-Z]*$")+ " " + Regex.IsMatch(fixedString1, @"^[0-9a-zA-Z]+$") + " " + Regex.IsMatch(fixedString1, @"^[0-9a-zA-Z]{1,17}$"));

        //Console.WriteLine(Regex.IsMatch(fixedString2, @"^[0-9a-zA-Z]*$")+ " " + Regex.IsMatch(fixedString2, @"^[0-9a-zA-Z]+$") + " " + Regex.IsMatch(fixedString2, @"^[0-9a-zA-Z]{1,17}$"));              

    }

}