protected override bool Exists(string key)
        {
            return AspectF.Define.
                Cache<bool>(m_DictionaryCache, key).
                Return(() =>
                    {
                        string path = GetFileName(key, false) + "*";
                        string[] fileNames = m_Store.GetFileNames(path);
                        foreach (string fileName in fileNames)
                        {
                            using (IsolatedStorageFileStream isoFile = new IsolatedStorageFileStream(Path.Combine(WorkFolderPath, fileName),
                                FileMode.Open, FileAccess.Read, m_Store))
                            {
                                string content = isoFile.ReadToEnd();
                                if (content == key)
                                {
                                    return true;
                                }
                            }
                        }

                        return false;
                    });
        }