Angular2无法在Web Api (asp.net核心)上发布对象

import { HttpClient, HttpHeaders } from '@angular/common/http';

// ...

constructor(private http: HttpClient) {}

// ...

let obj = { name: 'John', age: 30 };
let jsonStr = JSON.stringify(obj);

let headers = new HttpHeaders({ 'Content-Type': 'application/json' });

this.http.post('api/endpoint', jsonStr, { headers: headers }).subscribe(
  response => {
    console.log(response);
  },
  error => {
    console.error(error);
  }
);

using Newtonsoft.Json;

// ...

[HttpPost("api/endpoint")]
public IActionResult Endpoint([FromBody] string jsonStr)
{
    var obj = JsonConvert.DeserializeObject(jsonStr);
    
    // Process the object
    
    return Ok();
}