AvailableFileName

        public static string AvailableFileName(string fileName)
        {
            if (!File.Exists(fileName))
            {
                return fileName;
            }
            string str = Path.Combine(Path.GetDirectoryName(fileName), Path.GetFileNameWithoutExtension(fileName));
            string extension = Path.GetExtension(fileName);
            int num = 1;
            while (true)
            {
                string path = string.Format("{0}({1}){2}", str, num, extension);
                if (!File.Exists(path))
                {
                    return path;
                }
                num++;
            }
        }