verify-google-recaptcha.cs

/*
A function to verify Google reCAPTCHA (server side integration)
*/
protected bool VerifyRecaptcha()
{
    var values = new Dictionary<string, string>
    {
        { "secret", ConfigurationManager.AppSettings["recaptcha:SecretKey"] },
        { "response", HttpContext.Request["g-recaptcha-response"] },
        { "remoteip", HttpContext.Request.UserHostAddress },
    };

    var content = new FormUrlEncodedContent(values);
    var client = new HttpClient();
    var response = Task.Run(() => client.PostAsync("https://www.google.com/recaptcha/api/siteverify", content)).Result;
    var responseString = Task.Run(() => response.Content.ReadAsStringAsync()).Result;
    dynamic recaptchaResult = JsonConvert.DeserializeObject(responseString);
    string success = recaptchaResult.success;

    return success.ToLower() == "true";
}