asp.net获取真实ip的方法

public string getip()
{
 string result = HttpContext.Current.Request.ServerVariables["HTTP_X_FORWARDED_FOR"];
 if (null == result || result == String.Empty)
 {
 result = HttpContext.Current.Request.ServerVariables["REMOTE_ADDR"];
 }
 if (null == result || result == String.Empty)
 {
 result = HttpContext.Current.Request.UserHostAddress;
 }
 return result;
}