MapView:GraphicsOverlays is a GraphicsOverlayCollection which has a CopyTo method. This would be similiar to a Clone. You create a new array and then copy into that array and then you can assign the new GraphicsOverlayCollection to the overview MapView
LayerCollection operationalLayers = new LayerCollection();
Layer[] tempLayers = new Layer[map.OperationalLayers.Count];
map.OperationalLayers.CopyTo(tempLayers, 0);
foreach (var operationalLayer in tempLayers)
{
map.OperationalLayers.Remove(operationalLayer);
operationalLayers.Add(operationalLayer);
}
The above is done to replace the OperationalLayers in a map, but the general idea is the same, just using GraphicOverlays. Instead of the .Remove, .Add like above use the temp array and add them to you other MapView
Thanks,
-Joe