title: How to use System.Windows.Forms in .NET Core class library
body: <p>I've created .NET Core class library and try to build it against net40 framework. I want to use Clipboard class from System.Windows.Forms assembly. How can I do this?</p>
  
  <p>My project.json file:</p>
  
  <pre><code>{
      "version": "1.0.0-*",
  
      "dependencies": {
          "NETStandard.Library": "1.6.0"
      },
  
      "frameworks": {
          "netstandard1.6": {
              "imports": "dnxcore50",
              "buildOptions": {
                  "define": [
                      "NETCORE"
                  ]
              },
              "dependencies": {
                  "System.Threading": "4.0.11",
                  "System.Threading.Thread": "4.0.0",
                  "System.Threading.Tasks":  "4.0.11"
                  }
          },
          "net40": {
              "buildOptions": {
                  "define": [
                      "NET40"
                      ]
                  },
              "dependencies": {
                  // dependency should be here but there is no such dll
              }
          }
      }
  }
  </code></pre>
  
  <p>All my net40 specific code is under NET40 define. Any thoughts?</p>