C#服务器端获取客户端IP的方法

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

/// <summary>
/// IPAddress 的摘要说明
/// </summary>
public static class IPAddress
{
    public static string getIPAddress(bool isAll)
    {
        string result = string.Empty;

        result = HttpContext.Current.Request.ServerVariables["HTTP_X_FORWARDED_FOR"];
        if (!isAll)
        {
            if (!string.IsNullOrEmpty(result))
            {
                //可能有代理
                if (result.IndexOf(".") == -1)
                {
                    //没有“.”肯定是非IPv4格式
                    result = string.Empty;
                }
                else
                {
                    if (result.IndexOf(",") != -1)
                    {
                        //有“,”，估计多个代理。取第一个不是内网的IP。
                        result = result.Replace(" ", "").Replace("'", "");
                        string[] temparyip = result.Split(",;".ToCharArray());
                        for (int i = 0; i <= temparyip.Length - 1; 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.")
                            {
                                //找到不是内网的地址
                                return temparyip[i];
                            }
                        }
                    }
                    else if (IsIPAddress(result))
                    {
                        //代理即是IP格式
                        return result;
                    }
                    else
                    {
                        result = string.Empty;
                        //代理中的内容 非IP，取IP
                    }
                }
            }
        }
        if (string.IsNullOrEmpty(result))
        {
            result = HttpContext.Current.Request.ServerVariables["REMOTE_ADDR"];
        }

        if (string.IsNullOrEmpty(result))
        {
            result = HttpContext.Current.Request.UserHostAddress;
        }

        if (IsIPAddress(result))
            return result;
        else
            return null;
    }

    /// <summary>
    /// 判断是否是IP地址格式 0.0.0.0
    /// </summary>
    /// <param name="str1">待判断的IP地址</param>
    /// <returns>true or false</returns>
    public static bool IsIPAddress(string str1)
    {
        if (String.IsNullOrEmpty(str1) || str1.Length < 7 || str1.Length > 15)
        {
            return false;
        }

        //string regformat = @"^((2[0-4]\d|25[0-5]|[01]?\d\d?)\.){3}(2[0-4]\d|25[0-5]|[01]?\d\d?)$";

        //System.Text.RegularExpressions.Regex regex = new System.Text.RegularExpressions.Regex(regformat, System.Text.RegularExpressions.RegexOptions.IgnoreCase);
        //return regex.IsMatch(str1);
        return System.Text.RegularExpressions.Regex.IsMatch(str1, @"^((2[0-4]\d|25[0-5]|[01]?\d\d?)\.){3}(2[0-4]\d|25[0-5]|[01]?\d\d?)$");
    }

    public static string GetHostAddress()
    {
        string userHostAddress = HttpContext.Current.Request.UserHostAddress;
        if (string.IsNullOrEmpty(userHostAddress))
        {
            userHostAddress = HttpContext.Current.Request.ServerVariables["REMOTE_ADDR"];
        }
        //最后判断获取是否成功，并检查IP地址的格式（检查其格式非常重要）
        if (!string.IsNullOrEmpty(userHostAddress) && IsIPAddress(userHostAddress))
        {
            return userHostAddress;
        }
        return "127.0.0.1";

    }
}