使用Join在LINQ查询中进行分组和求和

Question

I have a query in C# and i need to group by this query for c.Same_invoice and sum the column price in the row grouped.

I know how to do group by and sum but i don't know the solution for my case, with a join and a large amount of data.

The actual code is:

var query = from c in snd.external_invoices.OrderByDescending(x => x.date)
            join o in snd.invoices on c.idexternal_invoices equals o.id_external_invoice
            select new{
               c.idexternal_invoices,
               c.businessname,
               o.number,
               c.message,
               c.price,
               c.date,
               c.iduser
            };

Thank to all

Answer 1

You can use something like:

var query = from c in snd.external_invoices.OrderByDescending(x => x.date)
            join o in snd.invoices on c.idexternal_invoices equals o.id_external_invoice into grouped
            select new{
               Invoice =grouped.key, Price = grouped.Sum(x => x.Price)};