title: Unable to use data annotations
body: <p>So here we are trying to get a handle on EF7 ahead of the game and I'm running into what I can only call madness.</p>
  
  <p>In EF6 I use annotations quite a bit and I am trying to carry that over into EF7 which according to the UnicornStore project this is totally valid, however I'm running into a problem wherein visual studio 2015 complains that I don't have a reference to the System.ComponentModel.DataAnnotations assembly. Fair enough, I add my reference to the assembly and now I get the following from DNX Core 5.0: </p>
  
  <pre><code>Error   CS0234  The type or namespace name 'DataAnnotations' does not exist in the namespace 'System.ComponentModel' (are you missing an assembly reference?) Lib.DNX Core 5.0
  </code></pre>
  
  <p>For the life of me I can't figure this out as to whats going on here, as when I look at the UnicornStore as my reference there's no reference to that assembly in the project.json, however there is a reference in the project.lock.json and as I understand it you're not supposed to edit that file.</p>
  
  <p>The big question what am I doing wrong? Why would DNX 4.5.x not complain about the reference and yet DNX Core 5.0 is? </p>