Passing Object rather than selectedIndex from Databound listbox

I'm having an issue when I try to pass the selectedIndex of my list from my "List" screen.

On my List screen I have the following binding:

Code Behind:

    lbPrograms.ItemsSource = App.ViewModel.Items;

XAML:

    <ListBox x:Name="lbPrograms" ItemsSource="{Binding Items}" SelectionChanged="lbPrograms_SelectionChanged">
        <ListBox.ItemTemplate>
            <DataTemplate>
                <StackPanel x:Name="DataTemplateStackPanel" Orientation="Horizontal">
                    <Image x:Name="ItemImage" Source="/images/ArrowImg.png" Height="43" Width="43" VerticalAlignment="Top" Margin="10,0,20,0"/>
                    <StackPanel>
                        <TextBlock x:Name="ItemText" Text="{Binding programName}" Margin="-2,-13,0,0" Style="{StaticResource PhoneTextExtraLargeStyle}"/>
                        <TextBlock x:Name="DetailsText" Text="{Binding createDate}" Margin="0,-6,0,3" Style="{StaticResource PhoneTextSubtleStyle}"/>
                        <TextBlock x:Name="programId" Text="{Binding programId}" Margin="0,-6,0,3" Style="{StaticResource PhoneTextSubtleStyle}"/>
                    </StackPanel>
                    <!--<Image x:Name="ItemFavs" Source="/images/favs.png" Height="43" Width="43" VerticalAlignment="Top" Margin="10,0,20,0"/>
                    <Image x:Name="ItemDelete" Source="/images/delete.png" Height="43" Width="43" VerticalAlignment="Top" Margin="10,0,20,0"/>-->
                </StackPanel>
            </DataTemplate>
        </ListBox.ItemTemplate>
    </ListBox>

In my detail screen I look up using the selectedIndex value:

            App.ViewModel.Refresh();
            DataContext = App.ViewModel.Items[index].nValDictionary;

However, since I can't figure out how to just update a value in my iEnumerable collection I have been removingAt[index] and then re-adding to the collection. So can anyone tell me, how do use update an existing element in my collection? If not, can I pass the programId (that is in my binding) instead of the selectedIndex as the indexes are getting all messed up after the Delete/Add functionality.

Please Advise.

UPDATE:

After speaking in several forums I should clear up that I am implement INotifyChanged Event on my properties in my object.

Basically the following snippet of code is my current issue:

private void FavBtn_Click(object sender, EventArgs e)
{
    foreach (var item in App.ViewModel.Items)
    {
        if ((item.currentProgram == true) && (item.programId != index))
        {
            item.currentProgram = false;
        }

        if (item.programId == index)
        {
            item.currentProgram = true;
        }
    }

When I run this everything looks to be ok.

However, when I navigate to ano开发者_开发技巧ther page, I re-load the object and the changes are lost. It is almost like I need to save them before navigating, however, if I do a item.Save(); I get duplicates in my list.

---

I'm guessing you haven't implemented INotifyPropertyChanged on your Items class yet.

Implementing this will allow updates made in these objects to be updated through your data bindings.

Here's a walkthrough on how to implement INotifyPropertyChanged.

How to: Implement the INotifyPropertyChanged Interface

---

Is App.ViewModel.Items of type ObservableCollection<T>?

If so, when you modify a property of one of the collection items and raise a property change event (via INotifyPropertyChanged) indicating the collection property that your ListBox.ItemsSource is bound to, the DataTemplate bindings will do the rest.