score:0

string newdate = datetime.now.adddays(-30).tostring();

score:1

datetime newdate = datetime.now.adddays(-30);

var queryresultpage = (from r in customplanning
                       where (r.assignment == "in use") && (r.lastlogontimestamp != null && r.lastlogontimestamp != string.empty) 
                       &&  (r.cust_shrt_nm != null) 
                       && !(from ua in surveyactivity where ua.customdemandid == r.id select ua.customdemandid).contains(r.id)
                       select r).orderby(t => t.id).tolist();
queryresultpage = queryresultpage.where(r => system.convert.todatetime(r.lastlogontimestamp) < newdate).tolist();

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