private static readonly AwaitableCriticalSection _criticalSection = new AwaitableCriticalSection();

        public static async Task<T> ReadJsonExCs<T>(String fileName)
        {
            if (String.IsNullOrEmpty(fileName))
                return default(T);

            return await await Task.Factory.StartNew(async () =>
            {
                using (var section = await _criticalSection.EnterAsync())
                using (var store = IsolatedStorageFile.GetUserStoreForApplication())
                using (var stream = new IsolatedStorageFileStream(fileName, FileMode.Open, store))
                using (var sr = new StreamReader(stream))
                using (var jr = new JsonTextReader(sr))
                    return await jr.ReadJsonAsyncTask<T>();
            });
        }

        public static async Task<bool> WriteJsonExCs<T>(String fileName, T content)
        {
            if (String.IsNullOrEmpty(fileName))
                return false;

            return await await Task.Factory.StartNew(async () =>
            {
                using (var section = await _criticalSection.EnterAsync())
                using (var store = IsolatedStorageFile.GetUserStoreForApplication())
                {
                    store.CreateFolderIfNecessary(fileName);

                    using (var stream = new IsolatedStorageFileStream(fileName, FileMode.Create, store))
                    using (var sw = new StreamWriter(stream))
                    using (var jw = new JsonTextWriter(sw))
                        await jw.WriteJsonAsyncTask(content);
                }

                return true;
            });
        }