PostAsync返回未经授权

Question

我遇到了一个奇怪的问题，我很确定自己的令牌（我使用Postman尝试了它。），但是它不适用于下面的C＃代码：

Env：ASP.NET Core 2.2

try
            {
                string _uri = "https://example.com/test";

                var _baseAddress = new Uri(_uri);

                using (var _client = new HttpClient() { BaseAddress = _baseAddress  })
                {
                    var _pairs = new { };

                    _client.DefaultRequestHeaders.Authorization = new System.Net.Http.Headers.AuthenticationHeaderValue("Bearer", _token);
                    _client.DefaultRequestHeaders.TryAddWithoutValidation("Content-Type", "application/json");
                    _client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));


                    var _response = _client.PostAsync("", _pairs.AsJson()).Result;
                    HttpStatusCode _statusCode = _response.StatusCode;
                }
            }
            catch (Exception _ex) { ClsMain.SaveErrorLog("Create:" + _ex.ToString()); }
            finally { }

我错过了什么？

请帮助