using System;

using System.Text.RegularExpressions;

public class Program

{

    public static void Main()

    {

        string line;

        do

        {

            Console.WriteLine("Enter a file name to validate it or -1 to exit");

            line = Console.ReadLine();

            Console.Clear();

            if (line != "-1") {

                if (ValidName(line))

                {

                    Console.WriteLine("File name {0}, is valid", line);

                }

                else

                {

                    Console.WriteLine("File name {0}, is INVALID", line);

                }

            }

​

        } while (line != "-1");

    }

    public static bool ValidName(string name)

    {

    return new Regex(@"^[0-9a-zA-Z\-_.()#@!-$%^&' ]+$").IsMatch(name);

    }

}