Google reCaptcha in Web API 2 c#

Question

I have an ASP.NET Web API 2 Project. I am trying to read Google Captcha from the form. I tried this Code:

    public string Post(FoundingRequest model)
    {
        var response = Request["g-recaptcha-response"];
        string secretKey = "my key";
        var client = new WebClient();
        var result = client.DownloadString(
        $"https://www.google.com/recaptcha/api/siteverify?secret={secretKey}&response={response}");
        var obj = JObject.Parse(result);
        model.Captcha = (bool)obj.SelectToken("success");
        ....
    }

but I am receiving an Error on the first line:

Cannot apply indexing with [] to an expression of type 'HttpRequestMessage'

why? and how to solve it? thank you

Answer 1

I found the answer, I created a hidden input with a certain name and updated its value on Captcha call back. Code:

   <input type="hidden" value="" id="recaptcha" name="recaptcha" />
   <div class="g-recaptcha" data-callback="imNotARobot" data-sitekey="key"></div>

and the Javascript is:

<script type="text/javascript">
    var imNotARobot = function () {
       $("#recaptcha").val(grecaptcha.getResponse());
    };
</script>

server side:

public string Recaptcha { get; set; }

and the model binder does all the work.