LINQ - group/sum multiple columns

Question

Data is a local CSV file that is loaded into an ado.net dataset via OleDB. The table has 40+ columns consisting of invoice details. Each row is a separate line item within an in

Answer 1

You are, in fact, only doing one query when you use the results of invoiceTotals. In the code you are showing you are even not doing a query on the database.

Google "linq deferred execution", it's nifty ;-)

But as Uriil says, you can just combine the statements into one linq query:

var invoiceSum =
DSZoho.Tables["Invoices"].AsEnumerable()
.Select (x => 
    new {  
        InvNumber = x["invoice number"],
        InvTotal = x["item price"],
        Contact = x["customer name"],
        InvDate = x["invoice date"],
        DueDate = x["due date"],
        Balance = x["balance"],
        }
 )
 .GroupBy (s => new {s.InvNumber, s.Contact, s.InvDate, s.DueDate} )
 .Select (g => 
        new {
            InvNumber = g.Key.InvNumber,
            InvDate = g.Key.InvDate,
            DueDate = g.Key.DueDate,
            Contact = g.Key.Contact,
            InvTotal = g.Sum (x => Math.Round(Convert.ToDecimal(x.InvTotal), 2)),
            Balance = g.Sum (x => Math.Round(Convert.ToDecimal(x.Balance), 2)),
            } 
 );