title: Is ConfigurationManager.AppSettings available in .NET Core 2.0?
body: <p>I've got a method that reads settings from my config file like this:</p>
  <pre><code>var value = ConfigurationManager.AppSettings[key];
  </code></pre>
  <p>It compiles fine when targeting .NET Standard 2.0 only.</p>
  <p>Now I need multiple targets, so I updated my project file with:</p>
  <pre><code>&lt;TargetFrameworks&gt;netcoreapp2.0;net461;netstandard2.0&lt;/TargetFrameworks&gt;
  </code></pre>
  <p>But now, the compilation fails for <code>netcoreapp2.0</code> with the following error message:</p>
  <blockquote>
  <p>Error CS0103  The name 'ConfigurationManager' does not exist in the current context   (netcoreapp2.0)</p>
  </blockquote>
  <p>Separately, I created a new .NET Core 2.0 console application (only targeting .NET Core 2.0 this time), but likewise there seems to be no <code>ConfigurationManager</code> under the namespace <code>System.Configuration</code>.</p>
  <p>I'm quite confused because it's available under .NET Standard 2.0, so I would expect it to be available in .NET Core 2.0, as .NET Core 2.0 is .NET Standard 2.0 compliant.</p>
  <p>What am I missing?</p>