private IfNoneMatchHeader(EntityTag entityTag)
        {
            entityTag.ThrowIfNull("entityTag");

            _entityTag = entityTag;
        }
        public static IfRangeHeader Parse(string headerValue)
        {
            if (headerValue == null)
            {
                return(null);
            }

            return(Regex.IsMatch(headerValue, CommonRegexPatterns.HttpDate) ? new IfRangeHeader(null, headerValue.ParseHttpDate()) : new IfRangeHeader(EntityTag.Parse(headerValue), null));
        }