net如何实现根据ip获取所在您当前所在的位置

public partial class Test_IP : System.Web.UI.Page{    protected void Page_Load(object sender, EventArgs e)    {        String user_IP = "";        if (Request.ServerVariables["HTTP_VIA"] != null)        {            user_IP = Request.ServerVariables["HTTP_X_FORWARDED_FOR"].ToString();        }        else        {            user_IP = Request.ServerVariables["REMOTE_ADDR"].ToString();        }                this.Label1.Text ="ip="+user_IP+",,,"+ IpLocation(user_IP);            }    private string m_Location = "", m_IpAddress = "", m_Response = "";    public string IpLocation(string ipAddress)    {        m_IpAddress = ipAddress.Trim();        string[] ip = ipAddress.Split('.');        ipAddress = ip[0] + "." + ip[1] + ".1.1";        WebClient client = new WebClient();        client.Encoding = System.Text.Encoding.GetEncoding("GB2312");        string url = "http://www.ip138.com/ips.asp";        string post = "ip=" + ipAddress + "&action=2";        client.Headers.Set("Content-Type", "application/x-www-form-urlencoded");        string response = client.UploadString(url, post);        m_Response = response;        string p = @"<li>参考数据一：(?<location>[^<>]+?)</li>";        Match match = Regex.Match(response, p);        m_Location = match.Groups["location"].Value.Trim();        return m_Location;    }    public string Location    {        get        {            return m_Location;        }    }    public string IpAddress    {        get        {            return m_IpAddress;        }    }    /// <summary>    /// 返回网络反馈原始数据    /// </summary>    public string Response    {        get        {            return m_Response;        }    }}
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http://webservice.webxml.com.cn/WebServices/IpAddressSearchWebService.asmx?op=getCountryCityByIp
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下个IP地址库，然后找。
1楼说的那个和珊瑚虫IP库都是比较常用的