title: Enabling DataAnnotations in full/core platforms of .NET Core
body: <p>I've created a .NET Core (package) library project, which has a class like this:</p>
  
  <pre><code>public class Subscriber //: Representation
  {
      [Required]
      public SubscriberDef Info;
      public Guid ProviderID;
  }
  </code></pre>
  
  <p>No matter what I do, the compiler is not happy with the <code>[Required]</code> attribute.  I'm constantly told this:</p>
  
  <pre><code>NET Framework 4.5.1 - Not Available
  NET Platform 5.4 - Available
  </code></pre>
  
  <p>My project.json initially looked like this:</p>
  
  <pre><code>"frameworks": {
    "net451": {
      "dependencies": {
        "WebApi.Hal": "2.6.0",
      }
    },
    "dotnet5.4": {
      "dependencies": {
        "Microsoft.CSharp": "4.0.1-beta-23516",
        "System.Collections": "4.0.11-beta-23516",
        "System.Linq": "4.0.1-beta-23516",
        "System.Runtime": "4.0.21-beta-23516",
        "System.Threading": "4.0.11-beta-23516",
      }
    }
  },
  "dependencies": {
    "Excqape": "0.7.0",
    "System.ComponentModel.Annotations": "4.0.11-beta-23516"
  }
  </code></pre>
  
  <p>I tried switching the target framework moniker (TFM) from <code>net451</code> to <code>net46</code>. No luck.  I tried different versions of System.ComponentModel.Annotations being used for both frameworks, still no luck.  </p>
  
  <p>What makes this particularly strange is that if I create an ASP.NET Core project, then I am free to have two frameworks where data annotation are respected and will compile:</p>
  
  <pre><code>"frameworks": {
    "dnx46": { },
    "dnxcore50": { }
  },
  </code></pre>
  
  <p>I figure if data annotations work inside of ASP.NET Core, then assuredly they would work in .NET Core as well?  </p>
  
  <p>Am I doing something wrong, or are data annotations truly unavailable for .NET Core fullCLR at this time?</p>