Add content to groupeditems page in Windows 8

When I create GroupedItemsPage it has DataModel / SampleDataSource.cs for example

but how can I add content that I download from the internet and modify with Fizzler?

 public sealed class SampleDataSource
  {
    string a = "";
    private static SampleDataSource _sampleDataSource = new SampleDataSource();

    private ObservableCollection<SampleDataGroup> _allGroups = new ObservableCollection<SampleDataGroup>();
    public ObservableCollection<SampleDataGroup> AllGroups
    {
        get { return this._allGroups; }
    }

    public static IEnumerable<SampleDataGroup> GetGroups(string uniqueId)
    {
        if (!uniqueId.Equals("AllGroups")) throw new ArgumentException("Only 'AllGroups' is supported as a collection of groups");

        return _sampleDataSource.AllGroups;
    }

    public static SampleDataGroup GetGroup(string uniqueId)
    {
        // Simple linear search is acceptable for small data sets
        var matches = _sampleDataSource.AllGroups.Where((group) => group.UniqueId.Equals(uniqueId));
        if (matches.Count() == 1) return matches.First();
        return null;
    }

    public static SampleDataItem GetItem(string uniqueId)
    {
        // Simple linear search is acceptable for small data sets
        var matches = _sampleDataSource.AllGroups.SelectMany(group => group.Items).Where((item) => item.UniqueId.Equals(uniqueId));
        if (matches.Count() == 1) return matches.First();
        return null;
    }

    public async Task<string> DownloadStringContent()
    {
        HttpClient client = new HttpClient();
        var response = await client.GetAsync(new Uri("http://www.google.com"));
        var result = await response.RequestMessage.Content.ReadAsStringAsync();

        return result;
    }

    public async void setA()
    {
        a = await DownloadStringContent();
        while (a == "") ;
    }

    public SampleDataSource()
    {
        setA();
        String ITEM_CONTENT = a;
        //String ITEM_CONTENT = String.Format("Item Content: {0}\n\n{0}\n\n{0}\n\n{0}\n\n{0}\n\n{0}\n\n{0}",
          //          "Curabitur class aliquam vestibulum nam curae maecenas sed integer cras phasellus suspendisse quisque donec dis praesent accumsan bibendum pellentesque condimentum adipiscing etiam consequat vivamus dictumst aliquam duis convallis scelerisque est parturient ullamcorper aliquet fusce suspendisse nunc hac eleifend amet blandit facilisi condimentum commodo scelerisque faucibus aenean ullamcorper ante mauris dignissim consectetuer nullam lorem vestibulum habitant conubia elementum pellentesque morbi facilisis arcu sollicitudin diam cubilia aptent vestibulum auctor eget dapibus pellentesque inceptos leo egestas interdum nulla consectetuer suspendisse adipiscing pellentesque proin lobortis sollicitudin augue elit mus congue fermentum parturient fringilla euismod feugiat");

        var group1 = new SampleDataGroup("Group-1",
                "Group Title: 1",
                "Group Subtitle: 1",
                "Assets/DarkGray.png",
                "Group Description: Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vivamus tempor scelerisque lorem in vehicula. Aliquam tincidunt, lacus ut sagittis tristique, turpis massa volutpat augue, eu rutrum ligula ante a ante");
        group1.Items.Add(new SampleDataItem("Group-1-Item-1",
                "Item Title: 1",
                "Item Subtitle: 1",
                "Assets/LightGray.png",
                "Item Description: Pellentesque porta, mauris quis interdum vehicula, urna sapien ultrices velit, nec venenatis dui odio in augue. Cras posuere, enim a cursus convallis, neque turpis malesuada erat, ut adipiscing neque tortor ac erat.",
                ITEM_CONTENT,
                group1));
        group1.Items.Add(new SampleDataItem("Group-1-Item-2",
                "Item Title: 2",
                "Item Subtitle: 2",
                "Assets/DarkGray.png",
                "Item Description: Pellentesque porta, mauris quis interdum vehicula, urna sapien ultrices velit, nec venenatis dui odio in augue. Cras posuere, enim a cursus convallis, neque turpis malesuada erat, ut adipiscing neque tortor ac erat.",
                ITEM_CONTENT,
                group1));
        group1.Items.Add(new SampleDataItem("Group-1-Item-3",
                "Item Title: 3",
                "Item Subtitle: 3",
                "Assets/MediumGray.png",
                "Item Description: Pellentesque porta, mauris quis interdum vehicula, urna sapien ultrices velit, nec venenatis dui odio in augue. Cras posuere, enim a cursus convallis, neque turpis malesuada erat, ut adipiscing neque tortor ac erat.",
                ITEM_CONTENT,
                group1));
        group1.Items.Add(new SampleDataItem("Group-1-Item-4",
                "Item Title: 4",
                "Item Subtitle: 4",
                "Assets/DarkGray.png",
                "Item Description: Pellentesque porta, mauris quis interdum vehicula, urna sapien ultrices velit, nec venenatis dui odio in augue. Cras posuere, enim a cursus convallis, neque turpis malesuada erat, ut adipiscing neque tortor ac erat.",
                ITEM_CONTENT,
                group1));
        group1.Items.Add(new SampleDataItem("Group-1-Item-5",
                "Item Title: 5",
                "Item Subtitle: 5",
                "Assets/MediumGray.png",
                "Item Description: Pellentesque porta, mauris quis interdum vehicula, urna sapien ultrices velit, nec venenatis dui odio in augue. Cras posuere, enim a cursus convallis, neque turpis malesuada erat, ut adipiscing neque tortor ac erat.",
                ITEM_CONTENT,
                group1));
        this.AllGroups.Add(group1);
    }
}

      

        
        
        
      

    

I want to change the string in SampleDataSource by loading the string from httpclient but nothing in

how do i deal with this? help me please