c# - Binding data in LongListSelector

Question

I am referring to the example here : http://dotnet.dzone.com/articles/using-longlistselector-control

Here is my code :

public class Chapters
    {
        private string mainTitle;

        public string MainTitle
        {
            get { return mainTitle; }
            set { mainTitle = value; }
        }

        private List<string> subTitle;

        public List<string> SubTitle
        {
            get { return subTitle; }
            set { subTitle = value; }
        }


    }

private static IEnumerable<HighwayCode> GetCityList()
        {
            return myList;
             // Which already contains data:

              MainTitle : Chapters
              subtitle : ABC
              subtitle : X

              MainTitle : Chapters Two
              subtitle : ASDF
              subtitle : GHIJK

        }

        public class GroupingLayer<TKey, TElement> : IGrouping<TKey, TElement>
        {

            private readonly IGrouping<TKey, TElement> grouping;

            public GroupingLayer(IGrouping<TKey, TElement> unit)
            {
                grouping = unit;
            }

            public TKey Key
            {
                get { return grouping.Key; }
            }

            public IEnumerator<TElement> GetEnumerator()
            {
                return grouping.GetEnumerator();
            }

            System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
            {
                return grouping.GetEnumerator();
            }
        }

XAML:

<phone:PhoneApplicationPage.Resources>
        <DataTemplate x:Key="GroupHeader">
            <Border Background="{StaticResource PhoneAccentBrush}" Margin="{StaticResource PhoneTouchTargetOverhang}" Padding="{StaticResource PhoneTouchTargetOverhang}">
                <TextBlock Text="{Binding Key}"/>
            </Border>
        </DataTemplate>

        <DataTemplate x:Key="ItemTmpl">
        <Grid>
            <TextBlock Style="{StaticResource PhoneTextLargeStyle}" 
                       Foreground="Black" 
                       Text="{Binding SubTitle}"></TextBlock>
        </Grid>
    </DataTemplate>
    </phone:PhoneApplicationPage.Resources>

<phone:LongListSelector x:Name="longListSelector"
                                    IsGroupingEnabled="True" LayoutMode="List" HideEmptyGroups="False"
                                    ItemTemplate="{StaticResource ItemTmpl}"
                                    GroupHeaderTemplate="{StaticResource GroupHeader}"/>

and i am setting it like this :

var selected = (from c in myList
                group c by c.MainTitle into n
                select new GroupingLayer<string, MyObject>(n)).ToList();

longListSelector.ItemsSource = selected;

But for me its only displaying the Main Title but Sub titles are not displaying at all.

What is wrong here ?

Answer 1

I believe you should set your items source to an observablecollection

I didn't do it exactly like you, but here is my xaml and here is a viewmodel for an app I build for the windows phone store.

I also believe it is key to clear and then set your items source on update. When I was building a WPF app, I seem to remember spending a lot of time trouble shooting the observablecollection not updating.