http://msmvps.com/blogs/carlosq/archive/2008/08/13/mz-tools-articles-series-howto-add-an-error-with-navigation-to-the-error-list-from-a-visual-studio-add-in.aspxIt is conspicuous that the EnvDTE80.ErrorItems collection introduced by VS 2005 lacks an Add method to add errors to the ErrorList, so it was a common belief, apparently even within Microsoft and also mine until recently that only SDK packages can addenCommunityServer 2008.5 SP2 (Build: 40407.4157)