Nirish,
I'm very sorry but I need to say this issue does exist in our SilverlightEdtion product; Marker and GeoPpup also are control, and we add the popup control into marker control container, so whatever you modify the z-index property of popup, the popup control is always under the marker. Here is workaround for you temporary, you could add MouseEnter and MouseLeave event to marker and add popup for the marker in the event handler manually, the code likes below:
void marker1_MouseLeave(object sender, System.Windows.Input.MouseEventArgs e) {
popup.Visibility = Visibility.Collapsed;
}
void marker1_MouseEnter(object sender, System.Windows.Input.MouseEventArgs e) {
popup = new GeoPopup(-94.558, 38.078);
PointShape screenPoint = Map1.ToScreenCoordinate(popup.Position);
popup.SetValue(Canvas.LeftProperty, screenPoint.X);
popup.SetValue(Canvas.TopProperty, screenPoint.Y);
popup.SetValue(Canvas.ZIndexProperty, 2000);
popup.Content = "hahahah";
Map1.Children.Add(popup);
popup.Visibility = Visibility.Visible;
}
Thanks,
Johnny