using System;

using System.Collections.Generic;

using System.Security.Cryptography;

using System.Text;

using System.Text.RegularExpressions;

using System.Web;

using System.Net;

using System.IO;

​

namespace Geocode {

​

  public class Program {

​

    public static void Main() {

        var keyString = "5g8LU3oILgIW209VDpgmSuqSnJo=";

        var urlString = "https://maps.googleapis.com/maps/api/geocode/json?address=New+York&client=gme-bureaurs";

        var signedUrl = Sign(urlString, keyString);

​

        Encoding encode = System.Text.Encoding.GetEncoding("utf-8");

        WebRequest request = WebRequest.Create(signedUrl);

        WebResponse response = request.GetResponse();

        String responseString = null;

        using (Stream stream = response.GetResponseStream())

        {

            StreamReader reader = new StreamReader(stream, Encoding.UTF8);

            responseString = reader.ReadToEnd();

        }

        Console.Write(responseString);

    }

    private static string Sign(string url, string keyString) {

      ASCIIEncoding encoding = new ASCIIEncoding();

​

      // converting key to bytes will throw an exception, need to replace '-' and '_' characters first.

      string usablePrivateKey = keyString.Replace("-", "+").Replace("_", "/");

      byte[] privateKeyBytes = Convert.FromBase64String(usablePrivateKey);

​

      Uri uri = new Uri(url);

      byte[] encodedPathAndQueryBytes = encoding.GetBytes(uri.LocalPath + uri.Query);

​

      // compute the hash

      HMACSHA1 algorithm = new HMACSHA1(privateKeyBytes);

      byte[] hash = algorithm.ComputeHash(encodedPathAndQueryBytes);

​

      // convert the bytes to string and make url-safe by replacing '+' and '/' characters

      string signature = Convert.ToBase64String(hash).Replace("+", "-").Replace("/", "_");

      // Add the signature to the existing URI.

      return uri.Scheme+"://"+uri.Host+uri.LocalPath + uri.Query +"&signature=" + signature;

    }

  }

}