I'm having trouble to get this work. I'm trying to do ajax post using javascript fetch, and always get status error 400. It works with ApiController but not with SurfaceController.

Here is the code, please help. Kind regards.

Home.chstml

    @using Umbraco.Cms.Web.Common.PublishedModels;
    @inherits Umbraco.Cms.Web.Common.Views.UmbracoViewPage<ContentModels.Home>
    @using ContentModels = Umbraco.Cms.Web.Common.PublishedModels;
    @{
        Layout = "Main.cshtml";
    }
    <div id="container"></div>





<script>
        function LoadPartialView() {
            fetch('/umbraco/surface/test/getpartialview')
            .then(response => response.ok ? response.text() : console.log('error', response))
            .then(content => document.getElementById('container').innerHTML = content)
            .catch(error => console.log('Request Failed:', error));    
        }

        LoadPartialView(); // Works

        function PostDummyData() {

            var data = {
                title: 'foo',
                body: 'bar',
                userId: 1,
            };

            fetch('/umbraco/surface/test/postdummydata', {
                method: 'POST',
                headers: {
                    'Content-Type': 'application/json',
                },
                body: JSON.stringify(data),
            })
            .then(response => response.ok ? response.json() : console.log('error', response))
            .then(json => console.log('Json Response:', json))
            .catch(error => console.log('Request failed:', error)); 
        }

        PostDummyData(); // Doesn't work

 function PostDummyDataApi() {

            var data = {
                title: 'foo',
                body: 'bar',
                userId: 1,
            };

            fetch('/umbraco/api/testo/postdummydata', {
                method: 'POST',
                headers: {
                    'Content-Type': 'application/json',
                },
                body: JSON.stringify(data),
            })
            .then(response => response.ok ? response.json() : console.log('error', response))
            .then(json => console.log('Json Response:', json))
            .catch(error => console.log('Request failed:', error)); 
        }

        PostDummyDataApi(); // works
    </script>

TestController.cs

using Microsoft.AspNetCore.Mvc;
using umb10.Models;
using Umbraco.Cms.Core.Cache;
using Umbraco.Cms.Core.Logging;
using Umbraco.Cms.Core.Routing;
using Umbraco.Cms.Core.Services;
using Umbraco.Cms.Core.Web;
using Umbraco.Cms.Infrastructure.Persistence;
using Umbraco.Cms.Web.Website.Controllers;

namespace umb10.Controllers
{
    public class TestController : SurfaceController
    {
        private readonly IUmbracoContextAccessor umbracoContextAccessor;
        private readonly IUmbracoDatabaseFactory databaseFactory;
        private readonly ServiceContext services;
        private readonly AppCaches appCaches;
        private readonly IProfilingLogger profilingLogger;
        private readonly IPublishedUrlProvider publishedUrlProvider;

        public TestController(IUmbracoContextAccessor umbracoContextAccessor, IUmbracoDatabaseFactory databaseFactory, ServiceContext services, AppCaches appCaches, IProfilingLogger profilingLogger, IPublishedUrlProvider publishedUrlProvider) : base(umbracoContextAccessor, databaseFactory, services, appCaches, profilingLogger, publishedUrlProvider)
        {
            this.umbracoContextAccessor = umbracoContextAccessor;
            this.databaseFactory = databaseFactory;
            this.services = services;
            this.appCaches = appCaches;
            this.profilingLogger = profilingLogger;
            this.publishedUrlProvider = publishedUrlProvider;

        }

        public IActionResult GetPartialView()
        {
            return PartialView("~/Views/Partials/Test.cshtml");
        }

        [HttpPost]
        public IActionResult PostDummyData(PostModel postModel)
        {            
            return Ok(postModel);
        }
    }

}

PostModel.cs

namespace umb10.Models
{
    public class PostModel
    {
        public string Title { get; set; }
        public string Body { get; set; }
        public int UserId { get; set; }
    }
}

Testo Api Controller

using Microsoft.AspNetCore.Mvc;
using umb10.Models;
using Umbraco.Cms.Web.Common.Controllers;

namespace umb10.Controllers
{
    public class TestoController : UmbracoApiController
    {
        public IActionResult GetPartialView()
        {
            return Content("~/Views/Partials/Test.cshtml");
        }

        [HttpPost]
        public IActionResult PostDummyData(PostModel postModel)
        {
            return Ok(postModel);
        }
    }
}