using System.IO;
    using System.Text;
    using System.Net;
    using System.Net.Security;
    using System.Security.Cryptography.X509Certificates;
    private const String host = "http://apis.5118.com";
    private const String path = "/keyword/google";
    private const String method = "POST";
    private const String apikey = "你要调用的接口apikey";
    static void Main(string[] args)
    {
        String querys = "";
        String bodys = "keyword=keyword&page_index=page_index";
        String url = host + path;
        HttpWebRequest httpRequest = null;
        HttpWebResponse httpResponse = null;
        if (0 < querys.Length)
        {
            url = url + "?" + querys;
        }
        if (host.Contains("https://"))
        {
            ServicePointManager.ServerCertificateValidationCallback = new RemoteCertificateValidationCallback(CheckValidationResult);
            httpRequest = (HttpWebRequest)WebRequest.CreateDefault(new Uri(url));
        }
        else
        {
            httpRequest = (HttpWebRequest)WebRequest.Create(url);
        }
        httpRequest.Method = method;
        httpRequest.Headers.Add("Authorization", apikey);
        //根据API的要求，定义相对应的Content-Type
        httpRequest.ContentType = "application/x-www-form-urlencoded; charset=UTF-8";
        if (0 < bodys.Length)
        {
            byte[] data = Encoding.UTF8.GetBytes(bodys);
            using (Stream stream = httpRequest.GetRequestStream())
            {
                stream.Write(data, 0, data.Length);
            }
        }
        try
        {
            httpResponse = (HttpWebResponse)httpRequest.GetResponse();
        }
        catch (WebException ex)
        {
            httpResponse = (HttpWebResponse)ex.Response;
        }
        Console.WriteLine(httpResponse.StatusCode);
        Console.WriteLine(httpResponse.Method);
        Console.WriteLine(httpResponse.Headers);
        Stream st = httpResponse.GetResponseStream();
        StreamReader reader = new StreamReader(st, Encoding.GetEncoding("utf-8"));
        Console.WriteLine(reader.ReadToEnd());
        Console.WriteLine("\n");
    }
    public static bool CheckValidationResult(object sender, X509Certificate certificate, X509Chain chain, SslPolicyErrors errors)
    {
        return true;
    }