c# - Linq union two tables where on has an extra column -

i using union combine 2 tables audit , message. both have same column names except audit has column called deletedate. try use union merge both table if deletedate not exist, sets deletedate method null. commented out trying work. when uncomment code, error. there work around? here code

    var audit = in _audit.getall()                        .where(a => a.pint == pint && a.createdate < startdate && (enddate == null || enddate > a.createdate))                        select new                        {                            a.mint,                            a.mid,                            a.desc,                            a.pstring,                            a.ptype,                            a.mtype,                            a.createdate,                            //    a.deletedate,                            a.pint                        };      var message = in _message.getall()            .where(a => a.partnerint == partnerint && a.createdate < startdate && (enddate == null || enddate > a.createdate))                   select new                   {                       a.mint,                       a.mid,                       a.desc,                       a.pstring,                       a.ptype,                       a.mtype,                       a.cdate,                       a.pint                   };      var test = in audit.union(message)                select new auditmessagesgroup                {                    mint = a.int,                    mid = a.id,                    desc = a.desc,                    pstring = a.pstring,                    ptype = a.payloadtype,                    messagetype = a.mtype,                    createdate = a.createdate,          //          deletedate = a.deletedate != null ? a.deletedate : null,                    pint = a.pint                 }; 

here error

    error   cs1929  'iqueryable<<anonymous type: int mint, guid   mid, string desc, string pstring, string ptype,   mtypes mtype, datetime createdate, datetime deletedate, int?   pint>>' not contain definition 'union' , best   extension method overload 'parallelenumerable.union<<anonymous type: int   mint, guid mid, string desc, string pstring, string   ptype, mtypes mtype, datetime createdate, int? pint>>  (parallelquery<<anonymous type: int mint, guid mid, string   desc, string pstring, string ptype, mtypes   mtype, datetime createdate, int? pint>>, ienumerable<<anonymous   type: int mint, guid mid, string desc, string   pstring, string ptype, mtypes mtype, datetime   createdate, int? pint>>)' requires receiver of type   'parallelquery<<anonymous type: int mint, guid mid, string   desc, string pstring, string ptype, mtypes   mtype, datetime createdate, int? pint>>'     

no can't. basic criteria on union column count must match b/w tables. can generate dummy column though bypass. like

considering a.deletedate datetime in audit change message be

var message = in _message.getall()        .where(a => a.partnerint == partnerint && a.createdate < startdate && (enddate == null || enddate > a.createdate))               select new               {                   a.mint,                   a.mid,                   a.desc,                   a.pstring,                   a.ptype,                   a.mtype,                   a.cdate,                   datetime.now, // dummy column                   a.pint               }; 

then can perform union