sample: how to use XPath for JSON easy with .net 4.0 and Google apps search images.

google_search_images_sample.cs

using System;
using System.Collections.Generic;
using System.Linq;

using System.Net;
using System.Runtime.Serialization.Json;
using System.Xml;
using System.Xml.Linq;
using System.Xml.XPath;
using System.Web;

namespace wrp.code_test
{
	public class google_search_images
	{
		public static IEnumerable<string> invoke(string q)
		{
			var i = new google_search_images(HttpUtility.UrlEncode(q));
			return i.invoke(0, new string[] { });
		}

		protected IEnumerable<string> invoke(uint start, IEnumerable<string> r)
		{
			XDocument x;
			using (var str = new WebClient().OpenRead(url(start)))
				x = XDocument.Load(JsonReaderWriterFactory.CreateJsonReader(str, new XmlDictionaryReaderQuotas()));

			var z = x.XPathSelectElements(xpath_urls).Select(e => { return e.Value; });

			return (x.XPathSelectElement(xpath_response_data).Attribute(xml_attribute_type_name).Value != xml_attribute_type_value_null)
			? invoke(start + rsz, r.Union(x.XPathSelectElements(xpath_urls).Select(e => { return e.Value; })))
			: r;
		}

		protected google_search_images(string q)
		{ url_base = "http://ajax.googleapis.com/ajax/services/search/images?v=" + v + "&hr=" + hr + "&rsz=" + rsz + "&q=" + q; }

		protected string url(uint start) { return url_base + "&start=" + start; }

		protected const string xml_attribute_type_name = "type";
		protected const string xml_attribute_type_value_null = "null";
		protected const string xpath_response_data = "/root/responseData";
		protected const string xpath_urls = "/root/responseData/results//url";

		protected string q = string.Empty;
		protected uint start = 0;
		protected uint rsz = 8;
		protected string hr = "ja";
		protected string v = "1.0";
		protected readonly string url_base;
	}
}

namespace code_test_dotnet
{
	class Program
	{
		static void Main(string[] args)
		{
			wrp.code_test.google_search_images.invoke("site:usagi.chalou.info")
				.AsParallel()
				.ForAll(e => { Console.WriteLine(e); });
		}
	}
}