http://msmvps.com/blogs/carlosq/archive/2008/06/06/empty-projectproperties4-and-projectconfigurationproperties4-interfaces-in-vslangproj90-dll.aspxAs you may know, while the general Visual Studio automation model uses the EnvDTE DLL series (EnvDTE.dll, EnvDTE80.dll, EnvDTE90.dll), there are some extension DLLs for the automation model of VB.NET and C#, the VSLangProj DLL series (VSLangProj.dll,enCommunityServer 2008.5 SP2 (Build: 40407.4157)