[C#] Ensure file name is unique at a given path (puts <filename (count).ext>)

Ensure file name does not exist

    private string EnsureFileNameDoesNotExist(string storagePath, string fileName)
        {
            while (System.IO.File.Exists(Path.Combine(storagePath, fileName)))
            {
                var extension = Path.GetExtension(fileName);
                var fileNameWithoutExtension = Path.GetFileNameWithoutExtension(fileName);

                var fileCountMarker = new Regex("\\((?<count>[0-9]+)\\)$");

                var matchResult = fileCountMarker.Match(fileNameWithoutExtension);

                if (matchResult.Success)
                {
                    int counter;
                    var matchValue = matchResult.Value;
                    if (Int32.TryParse(matchValue.Replace("(", String.Empty).Replace(")", String.Empty), out counter))
                    {
                        fileName = fileName.Replace(matchValue, String.Format("({0})", ++counter));
                    }
                }
                else
                {
                    fileName = String.Format("{0} (2){1}", fileNameWithoutExtension, extension);
                }
            }

            return fileName;
        }