这段代码怎么解释。。

Question

public static string GetIP()
{
string result = String.Empty;

        result = HttpContext.Current.Request.ServerVariables["HTTP_X_FORWARDED_FOR"];
        if (string.IsNullOrEmpty(result))
        {
            result = HttpContext.Current.Request.ServerVariables["REMOTE_ADDR"];
        }

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

        if (string.IsNullOrEmpty(result) || !Regex.IsMatch(result, 
        @"^((2[0-4]\d|25[0-5]|[01]?\d\d?)\.){3}(2[0-4]\d|25[0-5]|[01]?\d\d?)$"))
        {
            return "127.0.0.1";
        }

        return result;
    }

Answer 1

public static string GetIP()
{
string result = String.Empty;
result = HttpContext.Current.Request.ServerVariables["HTTP_X_FORWARDED_FOR"]; 如果有代理，返回代理服务器报告的原始ip（而不是代理主机的ip）
if (string.IsNullOrEmpty(result))
{
result = HttpContext.Current.Request.ServerVariables["REMOTE_ADDR"]; 返回主机ip
}

    if (string.IsNullOrEmpty(result))
    {
        result = HttpContext.Current.Request.UserHostAddress; 这一步实际上多余，UserHostAddress就是remote_addr
    }

    if (string.IsNullOrEmpty(result) || !Regex.IsMatch(result,  
    @"^((2[0-4]\d|25[0-5]|[01]?\d\d?)\.){3}(2[0-4]\d|25[0-5]|[01]?\d\d?)$")) 如果没有ip，比如说内网回环，那么返回127.0.0.1是对的，但是如果是ipv6 ip，这么返回是不对的。总之，这样写简单粗暴且欠考虑。
    {
        return "127.0.0.1";
    }

    return result;
}