错误“ObjectContent`1”类型无法序列化内容类型“application/json”的响应正文；字符集=utf-8'

Question

我正在编写一个 web api 来从数据库中获取我的所有用户，但它给出了这个错误 The 'ObjectContent 1' type failed to serialize the response body for content type 'application/json; charset=utf-8'. 我已经添加了 webapiconfig.cs 文件和 web api 的所有先决条件。

WebApi

using Atea.Azure.ApiManagement.Entities;
using Atea.Azure.ApiMangement.Business;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Net.Http;
using System.Web.Http;

namespace Azure_API_Delegation_Portal.Controllers
{
    public class ApisController : ApiController
    {
        private readonly IUserService _userService;

        public ApisController(IUserService userService)
        {
            _userService = userService;

        }

        // GET api/<controller>
        public IEnumerable<User> GetAllUsers()
        {
            return _userService.AllUser();
        }
    }
}

Answer 1

应该这样做：

public JsonResult GetAllUsers()

{
   return Json(_userService.AllUser(), JsonRequestBehavior.AllowGet)

}