"index out of range ..." error when querying AD?

I have a simple login form to authenticate users. A code segment looks like
this:

search.PropertiesToLoad.Add("cn");

search.PropertiesToLoad.Add("name");

search.PropertiesToLoad.Add("givenname");

search.PropertiesToLoad.Add("sn");

search.PropertiesToLoad.Add("mail");



SearchResult result = search.FindOne();

string fullname = (string)result.Properties["name"][0];

string uname = (string)result.Properties["cn"][0];

string firstname = (string)result.Properties["givenname"][0];

string lastname = (string)result.Properties["sn"][0];

string mmail = (string)result.Properties["mail"][0];





When I tested with several user accounts, some authenticated perfectly fine,
some threw the exception "Index was out of range. Must be non-negative and
less than the size of the collection. Parameter name: index" . The
exception was eventually traced to the " string mmail =
(string)result.Properties["mail"][0]; " statement. So is this because that
user has no email in AD? How best to handle this?



Am a newbie in this area. Any insight appreciate.


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