/// <summary>
        /// Populates the page with content passed during navigation.  Any saved state is also
        /// provided when recreating a page from a prior session.
        /// </summary>
        /// <param name="sender">
        /// The source of the event; typically <see cref="Common.NavigationHelper"/>
        /// </param>
        /// <param name="e">Event data that provides both the navigation parameter passed to
        /// <see cref="Frame.Navigate(Type, Object)"/> when this page was initially requested and
        /// a dictionary of state preserved by this page during an earlier
        /// session.  The state will be null the first time a page is visited.</param>
        private async void navigationHelper_LoadState(object sender, LoadStateEventArgs e)
        {


            ////  One drive authentication

            string clientId = "kZoNIQAeXdWUvxXcx2vyF1E72Rg03JRz";
            string returnUrl = "https://login.live.com/oauth20_authorize.srf";
            string[] scopes = { "onedrive.readwrite", "wl.offline_access", "wl.signin" };



            var oneDriveClient = OneDriveClientExtensions.GetClientUsingOnlineIdAuthenticator(scopes);

            await oneDriveClient.AuthenticateAsync();

            var item = await oneDriveClient
                     .Drive
                     .Root
                     .ItemWithPath("Music/test.mp3")
                     .Request()
                     .GetAsync();

            

            Debug.WriteLine(item.Audio.Duration);

            ////////



            group = await MusicDataSource.GetGroupAsync((String)e.NavigationParameter);
            this.DefaultViewModel["Group"] = group;
            this.DefaultViewModel["Items"] = group.Items;

            if (e.PageState == null)
            {
                this.itemListView.SelectedItem = null;
                // When this is a new page, select the first item automatically unless logical page
                // navigation is being used (see the logical page navigation #region below.)
                if (!this.UsingLogicalPageNavigation() && this.itemsViewSource.View != null)
                {
                    this.itemsViewSource.View.MoveCurrentToFirst();
                }
            }
            else
            {
                // Restore the previously saved state associated with this page
                if (e.PageState.ContainsKey("SelectedItem") && this.itemsViewSource.View != null)
                {
                    var selectedItem = await MusicDataSource.GetItemAsync((String)e.PageState["SelectedItem"]);
                    this.itemsViewSource.View.MoveCurrentTo(selectedItem);
                }
            }
        }
        private async Task GetMusicDataAsync()
        {
            string responseString = "";
           // string path = "http://www.shahmalav.com/api/tracks.json";
            string path = "http://76.228.72.40/tracks.json";
            dotest(path);

            if (this._groups.Count != 0)
                return;

            Uri uri = new Uri(path);

            HttpClient client = new HttpClient();

            HttpResponseMessage response = await client.GetAsync(uri);
            if (response.StatusCode == HttpStatusCode.OK)
            {
                responseString = await response.Content.ReadAsStringAsync();
            }
            
            /// test using local storage file
            /*
             StorageFile file = await StorageFile
             StorageFile file = await StorageFile.GetFileFromApplicationUriAsync(dataUri);
             string jsonText = await FileIO.ReadTextAsync(file);
             */

            string jsonText = responseString;
            JsonObject jsonObject = JsonObject.Parse(jsonText);
            JsonArray jsonArray = jsonObject["Groups"].GetArray();

            foreach (JsonValue groupValue in jsonArray)
            {
                JsonObject groupObject = groupValue.GetObject();
                MusicDataGroup group = new MusicDataGroup(groupObject["UniqueId"].GetString(),
                                                            groupObject["Title"].GetString(),
                                                            groupObject["Subtitle"].GetString(),
                                                            groupObject["ImagePath"].GetString(),
                                                            groupObject["Description"].GetString());

                foreach (JsonValue itemValue in groupObject["Items"].GetArray())
                {
                    JsonObject itemObject = itemValue.GetObject();
                    group.Items.Add(new MusicDataItem(itemObject["UniqueId"].GetString(),
                                                       itemObject["Title"].GetString(),
                                                       itemObject["Subtitle"].GetString(),
                                                       itemObject["ImagePath"].GetString(),
                                                       itemObject["Description"].GetString(),
                                                       itemObject["Content"].GetString()));
                }
                this.Groups.Add(group);
            }
        }