Autodesk Developer Network DevBlog: http://adndevblog.typepad.com/autocad/

kean‘s blog:http://through-the-interface.typepad.com/

autodesk c#.net forum:http://forums.autodesk.com/t5/NET/bd-p/152

autodesk .net api help:http://docs.autodesk.com/ACD/2013/ENU/index.html?url=files/GUID-4E1AAFA9-740E-4097-800C-CAED09CDFF12.htm,topicNumber=d30e712496

theSwamp forum:http://www.theswamp.org/

DXF:http://docs.autodesk.com/ACD/2014/ENU/index.html?url=files/GUID-235B22E0-A567-4CF6-92D3-38A2306D73F3.htm,topicNumber=d30e652301

AutoCAD Developer Center:http://usa.autodesk.com/adsk/servlet/index?id=1911627&siteID=123112