Questions about the code.

[mittnav]

I have a couple of questions that I would be happy if you like to answer, I can probably figure out the answers myself, but if you have the time and opportunity to answer, I would prefer that.

• This looks a bit strange, should it be like this?

public static bool operator <(MXRecord record1, MXRecord record2)
{
    if (record1.Preference > record2.Preference) return false;
    return false;
}

public static bool operator >(MXRecord record1, MXRecord record2)
{
    if (record1.Preference < record2.Preference) return false;
    return false;
}

• Maybe 'other' never can be null, but if, what should the return be, or is it better to throw in such an unusual case?

public int CompareTo(object? other)
{
    var mxOther = other as MXRecord;

    // we want to be able to sort them by preference
    if (mxOther?.Preference < Preference) return 1;
    if (mxOther?.Preference > Preference) return -1;

    // order mail servers of same preference by name
    return -string.CompareOrdinal(mxOther?.DomainName, DomainName);
}

• How sure can one be that 'Record' never becomes null? Could there be an appropriate default value?

  The problem finally ends here: Parallel.ForEach(res.Answers, answer => bag.Add(answer.Record));

  One can force a not null and tell there's not gonna be any nulls, but does one know that for a fact?