data binding content refreshing on pivotitem page - pivotitem

Question

I develop an application, and faced a problem with following part.
I have a 'textblock' that binds exact item in observable collection of items('Items') and shows the number. Each item has a property, called 'Count'.
When user taps current textblock, which is in stackpanel of longlistselector (binding Items), I need this textblock to show new number(idea is each time user taps textblock, number increases by 1).
The only method I discovered is each time Navigate to current pivot item(where textblock is situated) to force pivot item's reload data from observable collection, where updated items(and 'Count' property) are stored. But it is slow and doesn't work good.
Please, advice how to make the number appear in the textblock each time user taps on current textblock.
<phone:PivotItem Name="Documents" Header="Documents" Margin="0" >
<Grid>
<phone:LongListSelector ItemsSource="{Binding Items}" >
<phone:LongListSelector.ItemTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal"
Height="95" >
<TextBlock Tap="Plus_Tap" Visibility="Visible" Width="20" Height="50" Text="{Binding Count}" FontFamily="Segoe WP Light"
FontSize="35" Foreground="White" Margin="2,0,0,2"/>
</StackPanel>
</StackPanel>
</DataTemplate>
</phone:LongListSelector.ItemTemplate>
</phone:LongListSelector>
</Grid>
</phone:PivotItem>
namespace PackMan
{
public partial class CategoryList : PhoneApplicationPage
{
public CategoryList()
{
InitializeComponent();
DataContext = App.ViewModel;
}
protected override void OnNavigatedTo(NavigationEventArgs e)
{
if (!App.ViewModel.IsDataLoaded)
{
App.ViewModel.LoadData();
}
}
private void Plus_Tap(object sender, System.Windows.Input.GestureEventArgs e)
{
PackList selectedList = (sender as TextBlock).DataContext as PackList;
selectedList.Count += 1;
NavigationService.Navigate(new Uri("/CategoryList.xaml?Documents", UriKind.Relative));
}
}
}
How to refresh the data in pivot item after updating data through xaml UI?
here a guy in the very end of his posted answer to his own question wrote: "If you are using the observableCollection than no need to refresh the page. It is the magic of ViewModel." But I load data from 'Items' observable collection, which is not in ViewModel, but declared in Packlist.cs. Maybe this will help.
Here I do increase Count property of the item in ObservableCollection "Items" :
private void Plus_Tap(object sender, System.Windows.Input.GestureEventArgs e)
{
PackList selectedList = (sender as TextBlock).DataContext as PackList;
selectedList.Count += 1;
I tap on textblock, and text of the textblock shows no changes. I tap return - which brings me back to menu page, than again I open pivot item page, and see the textblock's text(number) increases by one. Change is seen only when I reload page(pivot item), since I have this in its constructor and OnNavigatedTo method:
public CategoryList()
{
InitializeComponent();
DataContext = App.ViewModel;
}
protected override void OnNavigatedTo(NavigationEventArgs e)
{
if (!App.ViewModel.IsDataLoaded)
{
App.ViewModel.LoadData();
}
}
LoadData() - loads OBservable collection ("Items"), which has items, and Count as one of its properties:
public void LoadData()
{
this.Items = LoadNewLists();
this.IsDataLoaded = true;
}
Maybe now you could tell me how to make text of the textblock change instantly as I tap on it(textblock). I will be thankful for any advice, since this moment has stopped me from developing my app second day now.

Answer 1

I figured it out. I should have read about INotifyPropertyChanged Interface and created 'Count' property using this interface's method:
public int Count
{
get
{
return _count;
}
set
{
if (value != _count)
{
_count = value;
NotifyPropertyChanged("Count");
}
}
}
public event PropertyChangedEventHandler PropertyChanged;
private void NotifyPropertyChanged(String propertyName)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (null != handler)
{
handler(this, new PropertyChangedEventArgs(propertyName));
}
}
Hope it will be helpful to anyone.