在C＃中使用HttpClient连接到salesforce时获得400 statusCode

Question

我正在尝试连接到salesforce沙箱环境，但我收到状态码400错误。以下是我的代码。

我的登录终点是：https://test.salesforce.com/services/oauth2/token

public Dictionary<string, string> Login()
        {
            String jsonResponse;

            using (var client = new HttpClient())
            {
                var request = new FormUrlEncodedContent(new Dictionary<string, string>
                {
                    {"grant_type", "password"},
                    {"client_id", clientId},
                    {"client_secret", clientSecret},
                    {"username", userName},
                    {"password", password}
                });

                request.Headers.Add("X-PrettyPrint", "1");

                var response = client.PostAsync(loginEndpoint, request).Result;
                jsonResponse = response.Content.ReadAsStringAsync().Result;
            }

            var values = JsonConvert.DeserializeObject<Dictionary<string, string>>(jsonResponse);
            return values;
        }