ASP.NETクライアントIPアドレス取得

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;
 
 
    /// <summary>
    ///      IP     0.0.0.0
    /// </summary>
    /// <param name="str1">    IP  </param>
    /// <returns>true or false</returns>
    public static bool IsIPAddress(string str1)
    {
        if (str1 == null || str1 == string.Empty || str1.Length < 7 || str1.Length > 15) return false;
        string regformat = @"^\d{1,3}[\.]\d{1,3}[\.]\d{1,3}[\.]\d{1,3}$";
        Regex regex = new Regex(regformat, RegexOptions.IgnoreCase);
        return regex.IsMatch(str1);
    }
 
    /// <summary> 
    ///        IP。                
    /// </summary> 
    public static string IPAddress
    {
        get
        {
            string result = String.Empty;
            result = HttpContext.Current.Request.ServerVariables["HTTP_X_FORWARDED_FOR"];
            if (result != null && result != String.Empty)
            {
                //      
                if (result.IndexOf(".") == -1)    //  “.”    IPv4   
                    result = null;
                else
                {
                    if (result.IndexOf(",") != -1)
                    {
                        // “,”，      。         IP。 
                        result = result.Replace(" ", "").Replace("'", "");
                        string[] temparyip = result.Split(",;".ToCharArray());
                        for (int i = 0; i < temparyip.Length; i++)
                        {
                            if (IsIPAddress(temparyip[i])
                                && temparyip[i].Substring(0, 3) != "10."
                                && temparyip[i].Substring(0, 7) != "192.168"
                                && temparyip[i].Substring(0, 7) != "172.16.")
                            {
                                return temparyip[i];    //          
                            }
                        }
                    }
                    else if (IsIPAddress(result)) //    IP   
                        return result;
                    else
                        result = null;    //        IP， IP 
                }
            }
            string IpAddress = (HttpContext.Current.Request.ServerVariables["HTTP_X_FORWARDED_FOR"] != null && HttpContext.Current.Request.ServerVariables["HTTP_X_FORWARDED_FOR"] != String.Empty) ? HttpContext.Current.Request.ServerVariables["HTTP_X_FORWARDED_FOR"] : HttpContext.Current.Request.ServerVariables["REMOTE_ADDR"];
 
            if (null == result || result == String.Empty)
                result = HttpContext.Current.Request.ServerVariables["REMOTE_ADDR"];
            if (result == null || result == String.Empty)
                result = HttpContext.Current.Request.UserHostAddress;
            return result;
        }
    }