LINQ query to select object and count

Question

I'm trying to do a query to generate packing slips, and need general order info, as well as how many items the order contains.

Here's my basic query:

var orders = (from cert in _orderRepository.GetAll()
                           where !cert.PrintedPackSlip
                           orderby cert.CardNumber
                           //group cert by cert.CardNumber
                           //into certGrp
                           select cert);

What I need to do is group by CardNumber and do a count of how many orders have that card number.

I would ideally it to come out like a Dictionary if at all possible

Are we talking about L2EF or L2SQL? If it's EF, see my question about a similar matter: stackoverflow.com/questions/10723439/… — walther
– walther, Commented Jul 5, 2012 at 19:06

Nick Jones · Accepted Answer · 2012-07-05 20:08:32Z

1

If I've correctly understood, for each order you want to list the total number of orders for that card number, in which case the following should work:

        var orders = (from cert in _orderRepository.GetAll()
                      join cert2 in _orderRepository.GetAll()
                      on cert.CardNumber equals cert2.CardNumber
                      where !cert.PrintedPackSlip 
                      where !cert2.PrintedPackSlip
                      group cert by cert
                      into certGrp
                      select certGrp).ToDictionary(o => o.Key,o => o.Count())

edited Jul 5, 2012 at 20:08

answered Jul 5, 2012 at 19:39

Nick Jones

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4 Comments

Matt Millican Over a year ago

It looks like it isn't possible to get the actual Order out of this, but only the key (or CardNumber)?

Nick Jones Over a year ago

Try changing it to .ToDictionary(o => o.First(),o => o.Count()) though that assumes that the first order in a group is representative of all the orders (without seeing the rest of the data which makes up an order I can't say if that is true)

Matt Millican Over a year ago

That would not be true. There could be multiple Orders that have the same card number, and we want to group those together to get the Count. Sorry if this is confusing. Thanks for the help though!

Nick Jones Over a year ago

OK, I think I know understand what you are trying to do - for each order you want to list the number of orders with the same card number - I've modified by answer to do this

Jeff Mercado · Accepted Answer · 2012-07-05 19:13:09Z

1

May be something like this:

var orders = from cert in _orderRepository.GetAll()
                       where !cert.PrintedPackSlip
                       orderby cert.CardNumber
                       group cert by cert.CardNumber into certGrp
                       select new {CardNumber = certGrp.Key, Count = certGrp.Count());

foreach(var item in orders)
    Console.WriteLine("item.CardNumber: " + item.CardNumber + " item.Count: " + item.Count.ToString());

edited Jul 5, 2012 at 19:13

Jeff Mercado

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answered Jul 5, 2012 at 19:10

Alex F

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3 Comments

Jeff Mercado Over a year ago

cert would be out of scope after the grouping, you'd have to use the key. I've made the correction.

Matt Millican Over a year ago

This is essentially what I had before, but I would ideally it to come out like a Dictionary<Order, int> if at all possible. (will add to question for clarification.

Arithmomaniac Over a year ago

@mmillican for a dictionary, just wrap this LINQ query in parentheses and append .ToDictionary<Order, int>(x => x.CardNumer, x => x.Count) to it.

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