C# 获取客户端IP

public string GetClientIP()
    {
        string sUserIP = string.Empty;
        if (Request.ServerVariables["HTTP_VIA"] != null)
        {
            // 穿过代理服务器取远程用户真实IP地址
            sUserIP = Request.ServerVariables["HTTP_X_FORWARDED_FOR"].ToString();
            if (string.IsNullOrEmpty(sUserIP))
                sUserIP = HttpContext.Current.Request.UserHostAddress;
            else
                sUserIP = Request.ServerVariables["REMOTE_ADDR"].ToString();
        }
        else
        {
            if (string.IsNullOrEmpty(sUserIP))
                sUserIP = HttpContext.Current.Request.UserHostAddress;
            else
                sUserIP = Request.ServerVariables["REMOTE_ADDR"].ToString();
        }
        return sUserIP;
    }