C# - Linq To SQL Updating Data?

I am just starting to use linq to sql for data access. It is working fine for read only. But it does not work for update. I have been reading the threads over several forums. It is clear that anonymous types (in my case var) cannot be updated. I cannot find what I should replace the var with and where I find it.

Below is the code. The exception is

Error 1 Property or indexer 'AnonymousType#1.date_last_logon' cannot be assigned to -- it is read only

fmcsaDataContext db = new fmcsaDataContext();
// DataTable _UserTable;
UserModel _UserModel = new UserModel();
var users = from u in db.FMCSA_USERs
where u.USER_NAME == pName && u.ACTIVE == true
select new
{
date_last_logon = u.DATE_LAST_LOGON,
date_current_logon = u.DATE_CURRENT_LOGON,
failed_login = u.FAILED_LOGIN,
};
if (users.Count() == 0)
return null;
foreach (var user in users)
{
user.date_last_logon = user.date_current_logon;
}