// invalidchars.cs using System; using System.IO; class InvalidChars { public static string ValidFileName (string s) { string valid = s; char[] invalidch = Path.GetInvalidFileNameChars(); foreach (char c in invalidch) { valid = valid.Replace(c, '_'); } return valid; } static void Main() { string badname = "this/is:bad|file?"; string goodname = ValidFileName(badname); Console.WriteLine(goodname); // 出力:this_is_bad_file_ } } // コンパイル方法:csc invalidchars.cs