该方法经过对各大门户网站测试结果是抓取率100%！

效果图

后台代码：

using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Text.RegularExpressions;
using System.Net;
using System.IO;
using System.Collections;

public partial class _Default : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{

}

}

protected void Button1_Click(object sender, EventArgs e)
{
TextBox2.Text = "";
string web_url = this.TextBox1.Text;//"http://blog.csdn.net/21aspnet/"
string all_code = "";
HttpWebRequest all_codeRequest = (HttpWebRequest)WebRequest.Create(web_url);
WebResponse all_codeResponse = all_codeRequest.GetResponse();
StreamReader the_Reader = new StreamReader(all_codeResponse.GetResponseStream());
all_code = the_Reader.ReadToEnd();
the_Reader.Close();
ArrayList my_list = new ArrayList();
string p = @"http://([\w-]+\.)+[\w-]+(/[\w- ./?%&=]*)?";
Regex re = new Regex(p, RegexOptions.IgnoreCase);
MatchCollection mc = re.Matches(all_code);

for (int i = 0; i <= mc.Count - 1; i++)
{
bool _foo = false;
string name = mc[i].ToString();
foreach (string list in my_list)
{
if (name == list)
{
_foo = true;
break;
}
}//过滤

if (!_foo)
{
TextBox2.Text += name + "\n";
}
}
}
}

前台
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %>

onClick="Button1_Click" Text="提取" />