title: The JSON value could not be converted to System.Nullable[System.Int32]
body: <p>I updated an ASP.NET Core 2.2 API to ASP.NET Core 3.0 and I am using System.Json:</p>
  
  <pre><code>services
    .AddMvc()
    .SetCompatibilityVersion(CompatibilityVersion.Version_3_0)
    .AddJsonOptions(x =&gt; {}) 
  </code></pre>
  
  <p>I then tried to post JSON data using Angular 8, which was working before:    </p>
  
  <pre><code>{
    "name": "John"
    "userId": "1"
  }
  </code></pre>
  
  <p>The model in the ASP.NET Core 3.0 API is:</p>
  
  <pre><code>public class UserModel {
    public String Name { get; set; }
    public Int32? UserId { get; set; } 
  }
  </code></pre>
  
  <p>And the API Controller action is as follows:</p>
  
  <pre><code>[HttpPost("users")]
  public async Task&lt;IActionResult&gt; Create([FromBody]PostModel) { 
  }
  </code></pre>
  
  <p>When I submit the model I get the following error:</p>
  
  <pre><code>The JSON value could not be converted to System.Nullable[System.Int32]. 
  </code></pre>
  
  <p>Do I need to do something else when using System.Json instead of Newtonsoft?</p>