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.