c# - Datetime? to string -

i need convert datetime? string. ?? operator dosent work , calling tostring on null make things fall over. advice on how handle datetime? thanks

below code context. o.customerrequireddate datetime? , predictedactivationdate string. both need stay datatype are.

 {        rsp = (from r in db.btrequests                                       join o in db.neworders                                       on r.id equals o.requestid                                       join s in db.status                                       on r.status equals s.id.tostring()                                       select new datalayer.orderresponse                                       {                                           requestid = requestid,                                           message = s.statusdescription,                                           orderstatus = r.status.tostring(),                                           predictedactivationdate =r.status == "3" || r.status == "4" || r.status == "5"                                           || r.status == "6" || r.status == "9" ? (o.customerrequireddate ?? ""): ""                                        }).firstordefault(); 

you do

o.customerrequireddate.hasvalue ? o.customerrequireddate.value.tostring() : ""