I'm using ArcObjects in C# .NET to create an ArcMap add-in for ArcGIS 10.2.1. I add the attached shape file as a layer to a document in ArcMap, enable Labels and set its Display Field to different fields, e.g. DETALJTYP. But the only field name that I can get programmatically from IFeatureLayer.DisplayField is EXTERNID, and I can't see why? It works fine with other layers. Any idea what's going on?