c# - Detect repeat and new customers -

i'm trying figure how write linq query return 2 lists of customers have checked in first time , didn't check in on given date

cusomters - name (nvarchar) - checkindate (datetime) 

i can write 2 separate queries, possible use single query?

this return 1 list of 2 kinds of customer want:

var result = customers.groupby(x=>x.name)                       .where(g=>g.count()==1 || !g.any(x=>x.checkindate == yourdate))                       .selectmany(x=>x); 

if want 2 lists, think work:

var result = customers.groupby(x=> customers.count(a=>a.name == x.name) == 1 ? 1 : 2)                       .select(g=> g.key == 1 ? g.tolist() : g.where(x=>!g.where(a=>a.checkindate == yourdate)                                                                          .any(a=>a.name == x.name)).tolist()); //to customers have first checked in var firstcheckedin = result[0]; //to customers didn't check in on given date var notcheckedin = result[1]  //or  var result = customers.groupby(x=> {                                     var c = customers.where(a=>a.name == x.name);                                     return c.count() == 1 ? 1 :                                            !c.any(a=>a.checkindate == yourdate) ? 2 : 3;                                    })                                                               .select(g=> g.tolist()).tolist();