提供空值的Response.header

Question

我在Angular 9.1.0和.net核心3.0.100上工作，在这方面我在respone.header.get(‘分页’)中得到空值。

当我从我的WebApi向postman发送呼叫时，显示正确的结果是post man header

下面是web Api的代码`

 public static void AddApplicationError(this HttpResponse response, string message)
        {
            response.Headers.Add("Application-Error",message);
            response.Headers.Add("Access-Control-Expose-Header","Application-Error");
            response.Headers.Add("Access-Control-Allow-Origin","*");
        }
        public static void AddPagination(this HttpResponse response, 
            int currentpage, int itemsPerPage, int totalItems, int totalpage)
        {
            var paginationHeader = new PaginationHeader(currentpage, itemsPerPage, totalItems, totalpage);
            var camelCaseFormetter = new JsonSerializerSettings();
            camelCaseFormetter.ContractResolver = new CamelCasePropertyNamesContractResolver();
            response.Headers.Add("pagination", 
                JsonConvert.SerializeObject(paginationHeader, camelCaseFormetter));
            response.Headers.Add("Access-Control-Expose-Header", "Pagination");
        }`

它会发送正确结果并添加报头。在StartUp.Cs类中，我添加了services.AddCors();，这是我的用户控制器函数`

[HttpGet]
        public async Task<IActionResult> GetUsers([FromQuery]UserPrams userPrams)
        {
            var user = await _repo.GetUsers(userPrams);
            var userToReturn = _mapper.Map<IEnumerable<UserForListDTO>>(user);
            Response.AddPagination(user.CurrentPage, user.PageSize, user.TotalCount, user.TotalPages);
            return Ok(userToReturn);
        }`

知道何时从angular应用程序发送请求，当报头中出现值时显示为null。这是Angular的代码

    getUsers(page?, itemsPerPage?): Observable<PaginatedResult<User[]>>
{
  const paginatedResult: PaginatedResult<User[]> = new PaginatedResult<User[]>();
  let params = new HttpParams();
  if (page != null && itemsPerPage != null)
  {
  params = params.append('pageNumber', page);
  params = params.append('pageSize', itemsPerPage);
}
  return this.http.get<User[]>(this.baseUrl + 'user', {observe: 'response', params })
  .pipe(
    map(response => {
      paginatedResult.result = response.body;
      if (response.headers.get('Pagination') != null)
      {
        paginatedResult.pagination = JSON.parse(response.headers.get('Pagination'));
      }
      return paginatedResult;
    })
  );
}

Chrome Header image请帮帮忙

Answer 1

你的angular前端应用程序托管在另一个域上吗？(CORS很重要吗？)如果是真的--也许这会有所帮助：

1. 我在邮递员响应中看不到Access-Control-Allow-Origin报头
2. By spec (rfc)报头名称不区分大小写。但angular实现可能与此规范不同，并且可能仅通过大小写匹配Access-Control-Expose-Header (使该值在响应头名称本身和Access-Control-Expose-Header中保持一致以消除这种可能性)