GMap.NET Windows Forms & Presentation is an excellent open source, powerful, free and cross-platform .NET control. Allows the use of routing, geocoding, directions and maps from Google, Yahoo!, Bing, OpenStreetMap, ArcGIS, Pergo, SigPac, Yendux, Mapy.cz, Maps.lt, iKarte.lv, NearMap, HereMap, CloudMade, WikiMapia, MapQuest and many more.
When geocoding fails, the OpenStreetMapProviderBase throws intern a null exception.
Shouldnt be better to check whether the address is null an set an ERROR code?