FileNameCharCheck, C#

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//Rextester.Program.Main is the entry point for your code. Don't change it.
//Compiler version 4.0.30319.17929 for Microsoft (R) .NET Framework 4.5

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;
using System.IO;

namespace Rextester
{
    public class Program
    {
        public static HashSet<char> InvalidNameChars = GetInvalidFileNameChars();
        public static HashSet<char> InvalidPathChars = new HashSet<char>(Path.GetInvalidPathChars());
        
        public static HashSet<char> GetInvalidFileNameChars()
        {
            char[] cs = Path.GetInvalidFileNameChars();
            HashSet<char> h = new HashSet<char>(cs);
            h.Remove(Path.DirectorySeparatorChar);
            return h;
        }
        
        /// <summary>
        /// Check if a string is valid for file name or not.
        /// </summary>
        /// <param name="s">file name string.</param>
        /// <returns>false if it contains invalid chars disallowed in file name or path.</returns>
        public static bool IsValid(string s)
        {
            if (s == null) return false;
        
            foreach (char c in s)
            {
                if (InvalidNameChars.Contains(c) || InvalidPathChars.Contains(c))
                {
                    return false;
                }
            }
        
            return true;
        }
        
        public static void Main(string[] args)
        {
            //Your code goes here
            Console.WriteLine("Hello, world!");
            string str = "監視サーバ01";
            Console.WriteLine(IsValid(str));
            
        }
    }
}

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Compilation time: 0,14 sec, absolute running time: 0,11 sec, cpu time: 0,09 sec, average memory usage: 14 Mb, average nr of threads: 3