Trouble binding LongListSelector.SelectedItem to MVVM property

Question

Using Visual Studio 2013 and the Window Phone 8 SDK I cannot get the SelectedItem property of the LongListSelector to properly bind to an MVVM property

Answer 1

Use bahavior

public class LongListSelectedItemBehavior : Behavior
{
    public object SelectedItem
    {
        get { return (object)GetValue(SelectedItemProperty); }
        set { SetValue(SelectedItemProperty, value); }
    }

    // Using a DependencyProperty as the backing store for SelectedItem.  This enables animation, styling, binding, etc...
    public static readonly DependencyProperty SelectedItemProperty =
        DependencyProperty.Register("SelectedItem", typeof(object), typeof(LongListSelectedItemBehavior), new PropertyMetadata(null));


    protected override void OnAttached()
    {
        base.OnAttached();

        if (AssociatedObject != null)
        {
            AssociatedObject.SelectionChanged += AssociatedObject_SelectionChanged;
        }
    }

    protected override void OnDetaching()
    {
        base.OnDetaching();

        if (AssociatedObject != null)
        {
            AssociatedObject.SelectionChanged -= AssociatedObject_SelectionChanged;
        }
    }

    private void AssociatedObject_SelectionChanged(object sender, System.Windows.Controls.SelectionChangedEventArgs e)
    {
        SelectedItem = AssociatedObject.SelectedItem;
    }

And XAML