GetURLPage

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading.Tasks;
using System.Web;

namespace CSharpConsole
{
    class ページ取得
    {
        static void Main(string[] args)
        {
            WebClient wc = new WebClient();
            Byte[] content = wc.DownloadData("http://esprogram.github.io/index.html");
            String s = Encoding.ASCII.GetString(content);
            Match encodeType = Regex.Match(s, @"<meta\s+[^>]*charset\s*=\s*([-_\w]+)", RegexOptions.IgnoreCase);
            String e = encodeType.Success ? encodeType.Groups[1].Value : "shift_jis";
            Encoding contentEncoding = Encoding.GetEncoding(e);
            Console.WriteLine(contentEncoding.GetString(content));
        }
    }
}