converting java code to c# code

package com.viadeo.servlets;
 
import java.io.BufferedReader;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
 
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
 
import org.json.JSONException;
import org.json.JSONObject;
 
public class Oauth2SampleCodeServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
	 
	private static final String clientId = "[your client id]";
	private static final String clientSecret = "[your client secret]";
	 
	private static final String oauthBase = "https://secure.viadeo.com/oauth-provider";
	private static final String authorizeURL = oauthBase + "/authorize2";
	private static final String accessTokenURL = oauthBase + "/access_token2";
	private static final String apiBase = "https://api.viadeo.com";
	 
	@Override
	protected void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
	 
		String code = request.getParameter("code");
		String redirectUri = request.getRequestURL().toString();
		 
		if (code == null || "".equals(code)) {
		 
			// Step 1 - Redirect user to provider for authorization
			String url = authorizeURL + "?response_type=code&display=popup&lang=en&client_id="
			+ clientId + "&redirect_uri=" + redirectUri;
			response.sendRedirect(url);
		 
		} else {
		 
			// Step 2 - Exchange for access grant
			String urlParameters = "grant_type=authorization_code&client_id=" + clientId
			+ "&client_secret=" + clientSecret
			+ "&redirect_uri=" + redirectUri + "&code=" + code;
			 
			String resp = executePost(accessTokenURL, urlParameters);
			 
			String accessToken = "";
			try {
				JSONObject json = new JSONObject(resp);
				accessToken = json.getString("access_token");
			} catch (JSONException e) { }
			 
			// Step 3 - Create connection
			response.setStatus(HttpServletResponse.SC_MOVED_TEMPORARILY);
			response.setHeader("Location", apiBase + "/me.xml?access_token=" + accessToken);
		}
	}
	 
	// POST request helper
	private String executePost(String targetURL, String urlParameters) {
	URL url;
	HttpURLConnection connection = null;
	try {
	// Create connection
	url = new URL(targetURL);
	connection = (HttpURLConnection) url.openConnection();
	connection.setRequestMethod("POST");
	connection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
	connection.setRequestProperty("Content-Length",
	"" + Integer.toString(urlParameters.getBytes().length));
	connection.setRequestProperty("Content-Language", "en-US");
	 
	connection.setUseCaches(false);
	connection.setDoInput(true);
	connection.setDoOutput(true);
	 
	// Send request
	DataOutputStream wr = new DataOutputStream(connection.getOutputStream());
	wr.writeBytes(urlParameters);
	wr.flush();
	wr.close();
	 
	// Get Response
	InputStream is = connection.getInputStream();
	BufferedReader rd = new BufferedReader(new InputStreamReader(is));
	String line;
	StringBuffer response = new StringBuffer();
	while ((line = rd.readLine()) != null) {
	response.append(line);
	response.append('\r');
	}
	rd.close();
	return response.toString();
	 
	} catch (Exception e) {
	e.printStackTrace();
	return null;
	} finally {
	if (connection != null) {
	connection.disconnect();
	}
	}
	}
}