Xamarin Forms - PostAsync 错误请求

Question

我正在尝试进行身份验证调用，无论我尝试什么，我都会收到 400，错误请求。这是我的代码：

        try
        {
            HttpClient myHttpClient = new HttpClient();
            client.DefaultRequestHeaders.Clear();
            client.DefaultRequestHeaders.Accept.Add(new System.Net.Http.Headers.MediaTypeWithQualityHeaderValue("application/json"));
            //client.DefaultRequestHeaders.TryAddWithoutValidation("Content-Type", "application/x-www-form-urlencoded");

            LoginApiRequestModel loginRequestModel = new LoginApiRequestModel()
            {
                Email = email,
                Password = password,
                UserScope = "restapi",
                ClientSecret = Constants.ClientSecret,
                GrantType = Constants.GrantType,
                ClientId = "5a8f011c-xxxx-xxxx"
            };

            var serializedLogin = JsonConvert.SerializeObject(loginRequestModel);
            var content = new StringContent(serializedLogin, Encoding.UTF8, "application/json");

            var response = await myHttpClient.PostAsync("https://xxxxxx/oauth/token", content);

            if (response.IsSuccessStatusCode)
            {
                using (var stream = await response.Content.ReadAsStreamAsync())
                using (var reader = new StreamReader(stream))
                using (var json = new JsonTextReader(reader))
                {
                    var jsoncontent = _serializer.Deserialize<LoginApiResponseModel>(json);

                    await SecureStorage.SetAsync("accessToken", jsoncontent.AccessToken);
                    await SecureStorage.SetAsync("refreshToken", jsoncontent.RefreshToken);
                    await SecureStorage.SetAsync("email", email);

                    return jsoncontent;
                }
            }
            else
            {
                var contents = response.Content.ReadAsStringAsync().Result;
                Debug.WriteLine(contents);

                return null;
            }
        }
        catch (Exception ex)
        {
            Debug.Write(ex);
            return null;
        }

我尝试过使用 SendAsync、所有可能的标头和编码类型，但没有任何效果。

我什至尝试过使用 Xcode、本机 iOS 进行调用，并且可以正常工作。这是我在 iOS 中的代码：

var headers = NetworkClient.defaultHeaders()
headers.add(name: "Content-Type", value: "application/x-www-form-urlencoded")
apiRequest(.authentication,
      parameters: params,
      encoding: URLEncoding.httpBody,
      headers: headers) { (result) in ...