Google Recaptcha verification

Using the Google Recaptcha verification API should be fairly straight forward. The one thing the documentation does not make clear is how to POST to the SiteVerify endpoint. So after playing around with the various options in Postman, I have found the following code works from the server side using C#.

                HttpClient httpClient = new HttpClient();

                KeyValuePair<string, string> secret = new KeyValuePair<string, string>("secret", recaptcha.Secret);
                KeyValuePair<string, string> response = new KeyValuePair<string, string>("response", recaptcha.Response);

                List<KeyValuePair<string, string>> postData = new List<KeyValuePair<string, string>>();

                using (var content = new FormUrlEncodedContent(postData))
                    content.Headers.Add("Content-Type", "application/x-www-form-urlencoded");

                    var recaptchaResponse = await httpClient.PostAsync(RecaptchaAPIUrl, content);

                    var returnValue = recaptchaResponse.Content.ReadAsStringAsync().Result;

                    var vr = JsonConvert.DeserializeObject<VerifiedResponse>(returnValue);

                    return this.Ok(vr);