title: Why a tuple doesn't have parameterless constructor while `[Serializable]`?
body: <p><code>System.Tuple(T1,..)</code> classes marked with <code>[SerializableAttribute]</code> (see <a href="https://msdn.microsoft.com/en-us/library/dd268536(v=vs.110).aspx" rel="nofollow noreferrer">msdn</a>). But they don't have a parameterless constructor so not serializable by <code>XmlSerializer</code> as it was cleared before at <a href="https://stackoverflow.com/questions/13739348/why-i-could-not-serialize-a-tuple-in-c">here</a>. So why not add one? </p>