Just to clarify, I'm not working C#. Just plain 'ol VB. In my case, "Config.esriaddinx" cannot be expanded. I had to modify a few things to make the walkthrough work. For example:ZoomToActiveLayerInTOC(TryCast(ArcMap.Application.Document, IMxDocument))
should beZoomToActiveLayerInTOC(TryCast(My.ArcMap.Application.Document, IMxDocument))
And:simpleMarkerSymbol.Style = esriSimpleMarkerStyle.esriSMSCircle
should besimpleMarkerSymbol.Style = ESRI.ArcGIS.Display.esriSimpleMarkerStyle.esriSMSCircle
I'm very new to VB and VS2008 so I'm actually not sure about everything going on here. But it works.