Custom WP7 Behaviors

ScrollPositionBehavior.cs

using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Interactivity;

namespace Custom.Behaviors
{
    public class ScrollPositionBehavior : Behavior<ScrollViewer>
    {
        public double Position
        {
            get { return (double)GetValue(PositionProperty); }
            set { SetValue(PositionProperty, value); }
        }

        public static readonly DependencyProperty PositionProperty = 
            DependencyProperty.Register("Position", typeof(double), typeof(ScrollPositionBehavior), new PropertyMetadata((double)0, OnPositionChanged));
        
        private ScrollViewer scrollViewer;

        protected override void OnAttached()
        {
            base.OnAttached();
            scrollViewer = AssociatedObject;
            scrollViewer.LayoutUpdated += (sender, args) =>
            {
                Position = scrollViewer.VerticalOffset;
            };
        }

        private static void OnPositionChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
        {
            var behavior = (ScrollPositionBehavior)sender;
            var value = (double)e.NewValue;
            if (Math.Abs(value - 0) < 0.00001)
            {
                behavior.AssociatedObject.ScrollToVerticalOffset(value); 
            }
        }

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

TrackablePivotBehavior.cs

using System.Windows;
using System.Windows.Controls;
using System.Windows.Interactivity;
using Microsoft.Phone.Controls;

namespace Custom.Behaviors
{
    public class TrackablePivotBehavior : Behavior<Pivot>
    {
        public static readonly DependencyProperty SelectedIndexProperty =
            DependencyProperty.Register("SelectedIndex", typeof(int), typeof(TrackablePivotBehavior), new PropertyMetadata(0, SelectedIndexPropertyChanged));

        private Pivot panarama;

        public int SelectedIndex
        {
            get { return (int)GetValue(SelectedIndexProperty); }
            set { SetValue(SelectedIndexProperty, value); }
        }

        private static void SelectedIndexPropertyChanged(DependencyObject dpObj, DependencyPropertyChangedEventArgs change)
        {
            if (change.NewValue.GetType() != typeof(int) || dpObj.GetType() != typeof(TrackablePivotBehavior))
                return;

            var track = (TrackablePivotBehavior)dpObj;

            Pivot pan = track.panarama;

            var index = (int)change.NewValue;

            if (pan.Items.Count > index)
                pan.SelectedIndex = (int)change.NewValue;
        }

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

            panarama = AssociatedObject;
            panarama.SelectionChanged += PanaramaSelectionChanged;
        }

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

            if (panarama != null)
                panarama.SelectionChanged += PanaramaSelectionChanged;
        }

        private void PanaramaSelectionChanged(object sender, SelectionChangedEventArgs e)
        {
            SelectedIndex = panarama.SelectedIndex;
        }
    }
}