http://blog.csdn.net/netjxz/archive/2007/10/28/1852343.aspx
http://blog.csdn.net/chenqi0701/archive/2008/03/04/2147309.aspx
BingMaps: http://blog.csdn.net/beniao277/archive/2010/04/07/5459527.aspx
private void MapWithPushpins_MouseDoubleClick(object sender, MapMouseEventArgs e)
{
// Disables the default mouse double-click action.
e.Handled = true;
// The location to place the pushpin at on the map.
Location pinLocation = MapWithPushpins.ViewportPointToLocation(e.ViewportPoint);
// The pushpin to add to the map.
Pushpin pin = new Pushpin();
pin.Location = pinLocation;
// Adds the pushpin to the map.
MapWithPushpins.Children.Add(pin);
}