I tried validate google recaptcha at server side, and according it's documentation, I had to do a request to an address (https://www.google.com/recaptcha/api/siteverify), passing three parameters (secret, response and remoteip).
I used the WebRequest class to make this request so I could get the validation response but I received an error (Request for the permission of type 'System.Net.WebPermission, System, Version=126.96.36.199, Culture=neutral, PublicKeyToken=b77a5c561934e089' failed)
I looked up other forums and it seems that sandboxed solutions, specifically do not allow requests to external websites and it screwed me because I wanted to put this solution on Office365. I searched on the web and I didn't find a valid solution that uses re-captcha to post information on forms.
Does anyone here knows how can I validate re-captcha at server side? Is there some configuration that I must do so I can finally, get the validation response?