There are many  domain checking websites available that gives all the information regarding domains. WhoIs is one of them. Following is a sample code that connects to one of WhoIs servers and retrieve information of a specific website.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Net.Sockets;
using System.IO;
using System.Text;
using System.Text.RegularExpressions;
public partial class _Default : System.Web.UI.Page
    protected void Page_Load(object sender, EventArgs e)
        string domainname = Request.QueryString["domain"].ToString();
        TcpClient objTCPC = new TcpClient();
        objTCPC.Connect("", 43);
        string strDomain = domainname;// +"\\r\\n";
        byte[] arrDomain = Encoding.ASCII.GetBytes(strDomain);
        Stream objStream = objTCPC.GetStream();
        objStream.Write(arrDomain, 0, strDomain.Length);
        StreamReader objSr = new StreamReader(objTCPC.GetStream(),Encoding.ASCII);
        string strServerResponse = objSr.ReadToEnd();
        strServerResponse = Regex.Replace(strServerResponse, "\n", "<br>");