// Yubico .NET client cliass that calls Yubico authentication server to
// validate an OTP (One-Time Password) generated by a Yubikey
//
// March 2008       
//
// Yubico.com - the elegant strong authentication built for the web


using System;
using System.Collections.Generic;
using System.Net;
using System.IO;
//using System.Web;

/// <summary>
/// Your app instantiate an object of this class, then call verify(OTP) to validate the
/// one-time password (OTP) generated by Yubikey
/// </summary>
public class YubicoClient
{
    const String YUBICO_AUTH_SRV_URL = "http://api.yubico.com/wsapi/verify?id=";

    private int _authId = -1;

    private String _response;

    //// Input param authId is assigned to you by Yubico. Each site operator has an authId
    // Eg. mashedLife.com authId is 28, dragonIPTV.com authId is 27, etc.
    // Contact tech@yubico.com if you haven't got an authId for your site.
    //
    public YubicoClient(int authId)
    {
        _authId = authId;
        _response = "";
    }

    //// Input param OTP is generated from your Yubikey when touching the button on it
    // 
    public Boolean verify(String otp)
    {
        Boolean result = false;

        _response = "";

        HttpWebRequest request = (HttpWebRequest)WebRequest.Create(
            YUBICO_AUTH_SRV_URL + _authId + "&otp=" + otp);
        HttpWebResponse response = (HttpWebResponse)request.GetResponse();
        String ver = response.ProtocolVersion.ToString();
        StreamReader reader = new StreamReader(response.GetResponseStream());
        string str = reader.ReadLine();
        while (str != null)
        {
            //Console.WriteLine(str);
            str = reader.ReadLine();
            _response += str + "\n";
            if (str.StartsWith("status="))
            {
                if (str.StartsWith("status=OK"))
                {
                    result = true;
                }
                break;
            }
        }
        return result;
    } // End of verify

    //// Useful to verify the cause of a validation error
    //
    String getLastResponse()
    {
        return _response;
    }

} // End of class YubicoClient

YubicoClient client = new YubicoClient(clientId, apiKey);
YubicoResponse response = client.verify(otp);
if(response.getStatus() == YubicoResponseStatus.OK) {
  // validation success
} else {
  // validation failure
}