I user to program ArcObjects using VB and then .Net. For such a simple piece of code (I used it before) as below: IMxDocument pDoc = m_app.Document as IMxDocument; IMap pMap = pDoc.FocusMap; ILayer pLayer; for (int i = 0; i < pMap.LayerCount; i++) { pLayer = pMap.Layer(i); // Got error // } Error 2 Non-invocable member 'ESRI.ArcGIS.Carto.IMap.Layer' cannot be used like a method. What's wrong with it? Thanks.