title: Attempting to use DbSet<TEntity>.Where() with EF7 and ASP.NET5
body: <p>I have created a solution with an ASP.NET 5 MVC6 project, and a few class libraries. I am using Visual Studio 2015, and I am targeting "dnxcore50" and "net451".</p>
  
  <p>In a class library I am writing the repository code with EF7. In a class I am attempting to use a few methods on DbSet&lt;>. Namely ".Where(...)", ".Single(...)" and ".First(...)". These were available on the older version of .NET.</p>
  
  <p>I am getting the following 2 errors:</p>
  
  <blockquote>
    <p>.NET Framework 4.5.1 error CS0012: The type 'IEnumerable&lt;>' is defined
    in an assembly that is not referenced. You must add a reference to
    assembly 'System.Runtime, Version=4.0.0.0, Culture=neutral,
    PublicKeyToken=b03f5f7f11d50a3a'.</p>
    
    <p>.NET Framework 4.5.1 error CS0012: The type 'Func&lt;,>' is defined in an
    assembly that is not referenced. You must add a reference to assembly
    'System.Runtime, Version=4.0.0.0, Culture=neutral,
    PublicKeyToken=b03f5f7f11d50a3a'.</p>
  </blockquote>
  
  <p>It seems to build no problem in DNXCORE50 format, but not the full 4.5.1 version of .NET.</p>
  
  <p>I have this in the project.json file:</p>
  
  <pre><code>"frameworks": {
      "net451": {
        "dependencies": {
          "System.Runtime": "4.0.21-beta-23516"
        }
      },
      "dnxcore50": {
        "dependencies": {
          "System.Runtime": "4.0.21-beta-23516"
          ......
        }
      }
    }
  </code></pre>
  
  <p>I am targetting 1.0.0-rc1-final DNX SDK version.</p>
  
  <p>Any ideas?</p>