CustomGoogleMapInfoWindow.cs

    public class CustomGoogleMapInfoWindow : Java.Lang.Object, GoogleMap.IInfoWindowAdapter
    {
        private Dictionary<string, ClusterItem> m_dicAllMarkerOnMap;
        
        public CustomGoogleMapInfoWindow(Activity context, Dictionary<string, ClusterItem> dicAllMarkerOnMap)
        {
            m_dicAllMarkerOnMap = dicAllMarkerOnMap;
            //...
        }
        
        //...
        
        public View GetInfoContents(Marker marker)
        {
            //...
            
            //Retrieve the ClusterItem associated to the marker
            ClusterItem clusterItem = null;
            m_dicAllMarkerOnMap.TryGetValue(m_currentMarker.Id, out clusterItem);

            //Add the custom information to the info window
            if (clusterItem != null)
                textviewDescription.Text += "\nMore info : " + clusterItem.m_sMoreCustomInformation;        
        }