Windows Phone 7.1 Two Way Binding doesn't seem to work

Question

First of all I feel really bad to ask this but I hope you can help me. I have a windows phone 7.1 one application with a progressbar. I would like to bind the progressbar TwoWay mode but I have tried a lot and could't find any solution.

ViewModel:

public class CollectionViewModel : INotifyPropertyChanged
{
    private bool _isLoading;

    public bool IsLoading 
    { 
        get { return _isLoading; }

        set
        {
            if (_isLoading != value)
            {
                _isLoading = value;

                NotifyPropertyChanged("IsLoading");
            }
        }
    }
}

In my PivotPage I bind an instance of my collectionViewModel to my PivotItem like this:

 public partial class Main_PivotPage : PhoneApplicationPage
 {
    CollectionViewModel _collectionViewModel;

    public Main_PivotPage()
    {
        InitializeComponent();
        _collectionViewModel = new CollectionViewModel();
        collectionPivotItem.DataContext = _collectionViewModel;
    }
}

Inside this pivotpage I have the ProgressBar that is bind to the IsLoading property.

XAML

 <ProgressBar IsIndeterminate="{Binding IsLoading, Mode=TwoWay}"/>

When I change the value of that property to true nothing will happen. The progressbar won't start loading.

Answer 1

Well, I didn't mention that I nested the progressbar into a listfooter. That was the problem. However the weird thing is, that the binded datacontext is working for my longlistselector but not for the listfooter in it. I had to bind the datacontext separately to the progressBar just like this:

collectionPivotItem.DataContext = _collectionViewModel;
        progressBar.DataContext = _collectionViewModel;

This solved my problem.