BelovApi/BelovAPI/Controllers/ChangeUser.cs

using BelovAPI.BaseConnection;
using BelovAPI.ModelBase;
using Microsoft.AspNetCore.Mvc;

namespace BelovAPI.Controllers
{
    [Route("api/[controller]")]
    [ApiController]
    [ApiExplorerSettings(GroupName = "Действия с пользователем")]
    public class ChangeUser : Controller
    {
        ApplicationContext db = new ApplicationContext();
        [HttpPut]
        public IActionResult Index(User NewUser, int id)
        {
            User user = db.User.FirstOrDefault(x => x.Id == id);
            user.nameUser = NewUser.nameUser;
            user.Age = NewUser.Age;
            db.SaveChanges();
            return Ok(user);
        }
    }
}