如何在Linq语句的多重联接中包含所有字段？

Question

var largeset =
from invs in context.Invoices
join lines in context.InvoiceLines on invs.InvoiceId equals lines.InvoiceId
join tracks in context.Tracks on lines.TrackId equals tracks.TrackId into grp
select new
          {
              Invoice = invs,
              Detail = grp
          };

In the above join into statement, Detail is a list but it only contains Invoice and Track columns. I want to be able to get columns from InvoiceLine as well.

Thanks in advance.

Answer 1

If you want to get the line info list for the invoice, you need to move the into to the first join and perform the other join inside the outer select .

Something like this:

var largeset =
    from inv in context.Invoices
    join line in context.InvoiceLines on inv.InvoiceId equals line.InvoiceId into lines
    select new
    {
        Invoice = inv,
        Lines =
            from line in lines
            join track in context.Tracks on line.TrackId equals track.TrackId
            select new { Line = line, Track = track }
    };

Answer 2

As an alternative to Ivan's solution which should yield better performance.

var largeset =
  from invs in context.Invoices
  join lines in context.InvoiceLines on invs.InvoiceId equals lines.InvoiceId
  join tracks in context.Tracks on lines.TrackId equals tracks.TrackId
  group new { invs, lines, tracks }
  by new
  {
      invs.InvoiceId,
      invs.InvoiceDate,
      invs.CustomerId,
      invs.Customer.LastName,
      invs.Customer.FirstName
  } into grp
  select new
  {
      InvoiceId = grp.Key.InvoiceId,
      InvoiceDate = grp.Key.InvoiceDate,
      CustomerId = grp.Key.CustomerId,
      CustomerLastName = grp.Key.LastName,
      CustomerFirstName = grp.Key.FirstName,
      CustomerFullName = grp.Key.LastName + ", " + grp.Key.FirstName,
      TotalQty = grp.Sum(l => l.lines.Quantity),
      TotalPrice = grp.Sum(l => l.lines.UnitPrice),
      Tracks = grp.Select(t => t.tracks)
  };