Pushpin location binding in windows phone 8 app is not working - dictionary

Question

i am developing a windows phone 8 app, in which i have to display a pushpin to current location.
while running the code it is showing an exception:
"An exception of type 'System.NullReferenceException' occurred in MapTestApp.DLL but was not handled in user code"
public MainPage()
{
InitializeComponent();
geolocator = new Geolocator();
geolocator.DesiredAccuracy = PositionAccuracy.High;
geolocator.MovementThreshold = 100; // The units are meters.
geolocator.StatusChanged += geolocator_StatusChanged;
geolocator.PositionChanged += geolocator_PositionChanged;
}
void geolocator_PositionChanged(Geolocator sender, PositionChangedEventArgs args)
{
Dispatcher.BeginInvoke(() =>
{
pushpin1.DataContext = args.Position.Coordinate;
});
}
.xaml code:
<maps:Map x:Name="MyMap" Center="{Binding}" ZoomLevel="15">
<toolkit:MapExtensions.Children>
<toolkit:Pushpin x:Name="pushpin1" GeoCoordinate="{Binding}">
<toolkit:Pushpin.Template>
<ControlTemplate TargetType="toolkit:Pushpin">
<StackPanel>
<ContentPresenter x:Name="content" Content="{TemplateBinding Content}" HorizontalAlignment="Left"></ContentPresenter>
<Path Data="M0,0L1,1L2,0L2,0L1,0L0,0Z"
Fill="#00AAFF"
Stretch="Fill"
Margin="-2,0"
Height="120"
Width="30"
Visibility="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=Content.Visibility, Mode=TwoWay}"
HorizontalAlignment="Left"
/>
</StackPanel>
</ControlTemplate>
</toolkit:Pushpin.Template>
</toolkit:Pushpin>
</toolkit:MapExtensions.Children>
</maps:Map>
Here is the link to the exception screen, it shows pushpin as null object: https://docs.google.com/file/d/0By0Y-Dca1cKjYXp4T3ctV1hLUEk/edit?usp=sharing

Answer 1

Please try this attached property
public static class PushPinExtension
{
public static readonly DependencyProperty ItemsSourceProperty = DependencyProperty.RegisterAttached("ItemsSource",
typeof(IEnumerable), typeof(PushPinExtension),
new PropertyMetadata(OnPushPinPropertyChanged));
private static void OnPushPinPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
var uie = (UIElement)d;
var pushpin = MapExtensions.GetChildren((Map)uie).OfType<MapItemsControl>().FirstOrDefault();
if (pushpin != null) pushpin.ItemsSource = (IEnumerable)e.NewValue;
}
public static IEnumerable GetItemsSource(DependencyObject obj)
{
return (IEnumerable)obj.GetValue(ItemsSourceProperty);
}
public static void SetItemsSource(DependencyObject obj, IEnumerable value)
{
obj.SetValue(ItemsSourceProperty, value);
}
}
dp:PushPinExtension.ItemsSource="{Binding Path=PushpinCollection}"