The R#'s ExtendSelection action fails to proeprly select identifiers containing underscores. The first selection is only the current part up to the underscore, and the next one is the whole line. The DEVENV's default action that's somehow similar to it, Edit.SelectCurrentWord, selects the identifier correctly. STR: An XmlDoc comment on some enum member, Trying to select GWLP_HWNDPARENT using the ExtendSelection action. On the first try, just GWLP or HWNDPARENT gets selected. On the second, the whole line (not including the ///). The first execution should select the whole identifier.