c# - linq - format string from two fields in select new context -

i have foreign table 1 many relation. write linq query left join equivalent , implement group relevant id field.

from p in db.personal join pn in   (from t in db.phonenumbers    group t t.personid g    select new { id = g.key,                  number = g.select(t => t.number),                  prefix = g.select(t => t.prefix)                }).asenumerable()    on p.id equals pn.id    lpn lpn in lpn.defaultifempty() //join wsd in db.basicoperations on p.id equals wsd.personid p.id == id.value select new partialpersondetailsviewmodel() {   id = id.value,   gendertype = p.gendertype,   sphonenumbers="(" +lpn.prefix+") "+lpn.number }).firstordefault(); 

but @ sphonenumbers="(" +lpn.prefix+") "+lpn.number place vs notify me error:

error 1 operator '+' cannot applied operands of type 'system.collections.generic.ienumerable' , 'system.collections.generic.ienumerable'

please me pass error , solve problem.

both of lpn.prefix , lpn.number evaluated g.select(...), in fact ienumerable<t> (exactly error message declares it).

evaluating them g.select(...).firstordefault() should since extract value of type t ienumerable<t>.

update:

in case, when lpn.prefix , lpn.number lists of values , need concatenate these lists - can use like:

sphonenumbers = string.join("; ",                              lpn.prefix.select((p, i) =>                               string.format("({0}){1}",                                              p,                                              lpn.numbers.skip(i).take(1).firstordefault()))); 

or can use enumerable.zip method, suggested in comments @chris:

sphonenumbers = string.join("; ",                             lpn.prefix.zip(lpn.numbers,                                           (s, s1) => string.format("({0}){1}", s, s1)));