Is there any way to make a MapPolyline have better performance on WP7

I'm currently using the Silverlight Map control for WP7, and am trying to visualize driving directions on the map. In order to highlight the route needed, I am using a MapLayer with a MapPolyline. The problem is that even with CacheMode set t开发者_C百科o BitmapCache, the MapPolyline area gets redrawn whenever the user pans or zooms the map. I've used other controls such as Ellipses or Pushpins, and with BitmapCache on, none of them redraw and give the same performance hit as MapPolyline.

Here's a quick example

    <maps:Map ZoomLevel="3">
        <maps:MapPolyline Name="line" Stroke="Red" StrokeThickness="9">
            <maps:MapPolyline.CacheMode>
                <BitmapCache/>
            </maps:MapPolyline.CacheMode>
            <maps:MapPolyline.Locations>
                <maps:LocationCollection>
                    <geo:GeoCoordinate Latitude="33" Longitude="33"/>
                    <geo:GeoCoordinate Latitude="36" Longitude="33"/>
                    <geo:GeoCoordinate Latitude="33" Longitude="36"/>
                </maps:LocationCollection>
            </maps:MapPolyline.Locations>
        </maps:MapPolyline>       
    </maps:Map>

If you set App.Current.Host.Settings.EnableRedrawRegions = true; you can see the redrawing that occurs. The performance is particularly bad when you have a larger polyline and zoom in closer.

Is there anything that can be done to help? The native Bing Maps has pretty smooth route drawing, so I would think that there should be a way to solve this?

Thanks!

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Can you explain a bit more what the problem is?

I've got an app - RunSat - in which I draw polylines with several hundred points (e.g. I just looked at a 3 hour long bike ride) and this draws fine - including during zoom operations.

I don't understand the problem - even using the sample code above. To help - are you testing on a phone or on the emulator?

As for CacheMode and BitmapCache, I'm really not sure about using these settings for the map - I don't use them in RunSat if that helps - I just leave the phone alone to work out its own GPU drawing.