title: Switch DNX Version in Visual Studio 2015?
body: <p>I started a new web project using dnu and dnx.  I was able to open it in Visual Studio and all was working great.  Now I installed the Facebook SDK nuget package, but it isn't compatible with DNX Core 5.0.  I have two sets of references, one for <code>DNX Core 5.0</code> and one for <code>DNX 4.5.1</code>.  When I compile I get errors because the types can't be found, although I can enter them fine in code and intellisense works.</p>
  
  <p>I can't find anywhere where the version is set.  In <code>global.json</code> it says my version is '1.0.0-rc1-final' which looks like 'clr' runtime, not 'coreclr'.  Does that mean it's 4.5.1?  It seems to have no relation to those versions.</p>
  
  <p><a href="https://i.stack.imgur.com/7L2sf.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/7L2sf.png" alt="dnvm versions"></a>  </p>
  
  <p>Looking in project.json I see facebook is there only for framework 'dnx451', if I add it to 'dnxcore50' then I get an error that Facebook 7.0.6 does not support DNXCore, Version=v5.0.</p>
  
  <pre><code>"frameworks": {
    "dnx451": {
      "dependencies": {
        "Facebook": "7.0.6"
      }
    },
    "dnxcore50": {
      "dependencies": {
        "Facebook": "7.0.6"
      }
    }
  },
  </code></pre>
  
  <p>A search of the entire project finds that this is the only place those strings exist.  Doing a recursive grep from the command line shows there are many lines with those strings in the paths (i.e. <code>lib/dnxcore50/</code>).  The parent seems to be <code>DNXCore,Version=v5.0</code>.</p>
  
  <p>Doing a full search for DNX I find web config has an httpPlatform entry:</p>
  
  <pre><code>    &lt;httpPlatform processPath="%DNX_PATH%"
           arguments="%DNX_ARGS%"
           stdoutLogEnabled="false"
           forwardWindowsAuthToken="false"
           startupTimeLimit="3600" /&gt;
  </code></pre>
  
  <p>How do I tell my project to use framework <code>dnx451</code>?  </p>