Sunny Portal signature generation method

gistfile1.cs

using System;
using System.Text;
using System.Security.Cryptography;
using System.Web;

namespace SPortal
{
	static class MainClass
	{

		public static string BuildSingature(String httpMethod, String apiService,
			String identifier, DateTime timestamp, String signatureSecretKey)
		{
			String sigString = httpMethod.ToLower () + apiService.ToLower () +
			                   timestamp.ToString ("s") + identifier.ToLower ();

			// NEW: UTF-8 inspite of ASCII
			UTF8Encoding encoder = new System.Text.UTF8Encoding();

			// string to byte[] for secret key
			byte[] encodedKey = encoder.GetBytes(signatureSecretKey);

			// string to byte[] for signature
			byte[] encodedSignature = encoder.GetBytes(sigString);

			// create hmacsha1
			HMACSHA1 hmacsha1 = new HMACSHA1(encodedKey);

			//create hash
			byte[] hmacHash = hmacsha1.ComputeHash(encodedSignature);

			// byte[] to base64
			String base64EncodedSignature = Convert.ToBase64String(hmacHash);

			// ... and URL encode
			String urlEncodeSignatureHashString = HttpUtility.UrlEncode(base64EncodedSignature);

			return urlEncodeSignatureHashString;
		}

		static void Main (string[] args)
		{
			DateTime datetimeNow = System.DateTime.Now;

			System.Console.WriteLine(datetimeNow);
			System.Console.WriteLine("SPortal signature key:");
			System.Console.WriteLine(BuildSingature("GET", "plantlist", "IDENTIFIER", datetimeNow, "KEY"));
		}
	}
}

http://www.sunnyportal.com API signature generation
Ruby implementation: https://gist.github.com/query-string/888c791d1f34748a0cbf