title: Error: Unexpected character encountered while parsing value: { using .NET core 3
body: <p>I don't understand why get an error "Unexpected character encountered while parsing value: {"?</p>
  
  <p>My startup config:</p>
  
  <pre><code>public void ConfigureServices(IServiceCollection services)
  {
      ...
  
      services.AddControllers().AddNewtonsoftJson(opts =&gt; {
              opts.SerializerSettings.ContractResolver = new CamelCasePropertyNamesContractResolver();
          }
      );
  }
  </code></pre>
  
  <p>My controller:</p>
  
  <pre><code>[HttpPost("{accountId}/top-up")]
  public async Task&lt;IActionResult&gt; TopUp([FromBody] decimal amount, [FromRoute] int accountId)
  {
      //...
  }
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/I3KYM.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/I3KYM.png" alt="enter image description here"></a><a href="https://i.stack.imgur.com/vAWXY.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/vAWXY.png" alt="enter image description here"></a></p>