You need a class to represent your json:
public class MyClass
{
public string Id { get; set; }
public string Item { get; set; }
}
Set a ObservableCollection property in your Form:
public ObservableCollection<MyClass> MyClassCollection { get; set; }
and then set the MyClassCollection property to your Deserialized json
MyClassCollection = JsonConvert.DeserializeObject<ObservableCollection<MyClass>>(e.Result);
That way you're binding your class list to the LongListSelector Control in your XAML:
<phone:LongListSelector Name="list" ItemsSource="{Binding MyClassCollection}">
<phone:LongListSelector.ItemTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal">
<TextBlock Text="{Binding id}" />
<TextBlock Text=" ( " />
<TextBlock Text="{Binding item}" FontStyle="Italic" />
<TextBlock Text=" )" />
</StackPanel>
</DataTemplate>
</phone:LongListSelector.ItemTemplate>
That should work.