title: Deserialize anonymous type with System.Text.Json
body: <p>I am updating some apps for .NET Core 3.x, and as part of that I'm trying to move from <code>Json.NET</code> to the new <code>System.Text.Json</code> classes. With Json.NET, I could deserialize an anonymous type like so:</p>
  
  <pre class="lang-cs prettyprint-override"><code>var token = JsonConvert.DeserializeAnonymousType(jsonStr, new { token = "" }).token;
  </code></pre>
  
  <p>Is there an equivalent method in the new namespace?</p>