Schengen visa has two basic rules: the first entry rule and the rule of the main host country .These rules are described in detail in the document governing visa issuance rules - you can find it on the website of any embassy: "Instructions on the competence of individual Schengen states in issuing a visa".This document clearly states that to enter not through the issuing country (and even more so stay in it) you must have good and convincing grounds .If there are no grounds, according to the Schengen Agreement instructions you may be denied entry ¥ $ .