WebClient位于System.Net命名空间下，通过这个类可以方便的创建Http请求并获取返回内容。

using System;
using System.Collections.Generic;
using System.Text;
using System.Net;
using System.IO;

namespace ConsoleWebClient
{
    class Program
    {
        static void Main(string[] args)
        {
            string uri = "http://www.cnblogs.com";
            WebClient wc = new WebClient();
            Stream st = wc.OpenRead(uri);
            StreamReader sr = new StreamReader(st);
            string res = sr.ReadToEnd();
            sr.Close();
            st.Close();
            Console.WriteLine(res);
            Console.ReadKey();
        }

        public void ReadPageContent()
        {
            string uri = "http://www.cnblogs.com";
            WebClient wc = new WebClient();
            byte[] bResponse = wc.DownloadData(uri);
            string strResponse = Encoding.UTF8.GetString(bResponse);
            Console.WriteLine(strResponse);
            Console.ReadKey();
        }
    }
}