c# - Linq Query with join on subquery -

basically i'm trying write query joins on select top 1 second table like:

select sum(pinfo.quantity + p.itemcount),     i.owner    invoice     join purchase_info pinfo       on pinfo.invoice = i.invid     join (select distinct sku,                           productlineid,                           itemcount             products productlineid in (13, 14)) p       on p.sku = pinfo.item  i.owner = 22623  group i.owner 

here's pathetic attempt in linq has invalid syntax, ideas appreciated.

(from in _invoicerepository.table  join pi in _purchaseinforepository.table on i.invoiceid equals pi.invoiceid  join p in (from p2 in _productrepository.table p2.sku == pi.item select new { p2.sku, p2.itemcount }).take(1)  on pi.item equals p.sku   i.memberid == memberid &&  (p.productlineid == (int)productlines.inkcartridges ||   p.productlineid == (int)productlines.tonercartridges)  select pi.quantity * p.itemcount) .defaultifempty(0) .sum(); 

here first stab @ this.

from sql, looks want find how many ink , toner cartridges particular customer has ordered ever.

this should give same results sql (this depending on order of products table since taking top 1 without sort of ordering being done:

  var count = in _invoicerepository.table               i.ownerid == memberid               select new                 {                   ownerid = i.ownerid,                   totalproductcount = i.purchases.sum(pro => pro.products                                                       .where(p => p.productlineid == (int)productlines.inkcartridges ||                                                          p.productlineid == (int)productlines.tonercartridges)                                                       .take(1)                                                       .sum(p => p.itemcount * pro.quantity))                 }; 

since did not know the classes of 3 objects (invoice, purchaseinfo, , product) made guess @ are:

invoice class: assume has list/collection of purchaseinfos

public class invoice {   public int id { get; set; }   public int ownerid { get; set; }    public list<purchaseinfo> purchases { get; set; } } 

purchaseinfos: invoice has multiple purchaseinfos, each 1 links (ideally) 1 product since sku not unique assome has list/collection of products in it.

public class purchaseinfo {   public int id { get; set; }   public int quantity { get; set; }    public int invoiceid { get; set; }   public invoice invoice { get; set; }    public int item {get;set;}   public list<product> products { get; set; } } 

product class: assome there id field (not shown) or composite primary key somewhere

public class product {   public int sku { get; set; }   public int productlineid { get; set; }   public int itemcount { get; set; }    public list<purchaseinfo> purchaseinfos { get; set; } } 

hopefully can take need. if way off, please update question class definitions (you can remove unneeded properities if want) better answer can produced.