C#获取IP地址

public string GetUserIP()
   {
        string _userIP;
       if(Request.ServerVariables["HTTP_VIA"] == null)
         {
              userIP= Request.UserHostAddress;
       }
      else
        {
          userIP= Request.ServerVariables["HTTP_X_FORWARDED_FOR"];
      }
      return userIP;
  }
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//下面这个比较全的 ，能够穿多层代理的，引用人的
    public static string IPAddress
    {
        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)    //没有“.”肯定是非IPv4格式
                    result = null;
                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; 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];    //找到不是内网的地址
                            }
                        }
                    }
                    else if ( IsIPAddress(result)) //代理即是IP格式
                        return result;
                    else
                        result = null;    //代理中的内容 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;
        }
    }

    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);