string IpAddress = "";

if((HttpContext.Current.Request.ServerVariables["HTTP_X_FORWARDED_FOR"]!=null
&& HttpContext.Current.Request.ServerVariables["HTTP_X_FORWARDED_FOR"] !=String.Empty) )
{
        IpAddress=HttpContext.Current.Request.ServerVariables["HTTP_X_FORWARDED_FOR"] ;
}
else
{
        HttpContext.Current.Request.ServerVariables["REMOTE_ADDR"];
}

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;
namespace Common
{
    /// <summary>
    /// IPAddress 的摘要說明
    /// </summary>
public class IPAddress : System.Web.UI.Page
{

    public static Int64 toDenaryIp ( string ip )
    {
        Int64 _Int64 = 0;
        string _ip = ip;
        if ( _ip.LastIndexOf ( "." ) > -1 )
        {
            string[] _iparray = _ip.Split ( '.' );

            _Int64 = Int64.Parse ( _iparray.GetValue ( 0 ).ToString() ) * 256 * 256 * 256 + Int64.Parse ( _iparray.GetValue ( 1 ).ToString() ) * 256 * 256 + Int64.Parse ( _iparray.GetValue ( 2 ).ToString() ) * 256 + Int64.Parse ( _iparray.GetValue ( 3 ).ToString() ) - 1;
        }
        return _Int64;
    }

    /// <summary>
    /// /ip十進制
    /// </summary>
    public static Int64 DenaryIp
    {
        get {
            Int64 _Int64 = 0;

            string _ip = IP;
            if ( _ip.LastIndexOf ( "." ) > -1 )
            {
                string[] _iparray= _ip.Split ( '.' );

                _Int64 = Int64.Parse ( _iparray.GetValue ( 0 ).ToString() ) * 256 * 256 * 256 + Int64.Parse ( _iparray.GetValue ( 1 ).ToString() ) * 256 * 256 + Int64.Parse ( _iparray.GetValue ( 2 ).ToString() ) * 256 + Int64.Parse ( _iparray.GetValue ( 3 ).ToString() )-1;
            }
            return _Int64;
        }
    }

    public static string IP
    {
        get
        {
            string result = String.Empty;
            result = HttpContext.Current.Request.ServerVariables["HTTP_X_FORWARDED_FOR"];
            if ( result != null && result != String.Empty )
            {
               //可能有代理
                if ( result.IndexOf ( "." ) == -1 ) //沒有"."肯定是非IPv4格式
                    result = null;
                else
                {
                    if ( result.IndexOf ( "," ) != -1 )
                    {
                         //有","，估計多個代理。取第一個不是內網的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]; //找到不是內網的地址
                            }
                        }
                    }
                    else if ( IsIPAddress ( result ) ) //代理即是IP格式
                        return result;
                    else
                        result = null; //代理中的內容 非IP，取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;
        }
    }

     //是否ip格式
    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 );
    }
}
}