c# linq orderby orders incorrectly or not in number seqence

Question

Hi

My numbers in my List do not order in strict sequence when using c# Linq. I can see a pattern but the numbers are not in the exact order that I need.

This is my c# Link code which has an orderby inside it ok :-

            //The Linq code which has an orderby within
            var cdbips = from cdb in CDBs
                         join ip in IPs
                         on cdb.Cdbno equals ip.Cdbno
                         where (cdb.Country == "Italy
                         orderby cdb.Cdbno ascending
                         select new classIP(cdb.Cdbno, ip.Ipno);
            foreach (var cdbip in cdbips)
            {
               CDBIPs.Add(cdbip);
            }
            DisplayCDBIPs();
        }
        private void DisplayCDBIPs()
        {
            listViewCDBIPs.Items.Clear();
            for (int i = 0; i < CDBIPs.Count; i++)
            {
                ListViewItem objListItem = listViewCDBIPs.Items.Add(CDBIPs[i].Cdbno);
                objListItem.SubItems.Add(CDBIPs[i].Ipno);
            }
        }

The output I see is :-

Thanks to anyone who can advise or help

Cheers

Matt

Answer 1

hi Norkk

Look at number 996 - it not in numeric order. I hope you can see what I mean now.

The order I would expect is as in the listview screenshot above but the 96 should be displayed at the top

Thanks

Matt

Answer 2

Yeah, i was not see that one, but i tried this example

            int[] arr = new int[] { 9601, 9663, 9738, 9777, 9801, 9817, 996, 9978 };

            var query = from row in arr
                        orderby row ascending
                        select row ;
            foreach (var n in query)
                Console.WriteLine(n);

Or this one

            var query = arr.OrderBy(row => row);
            foreach (var n in query)
                Console.WriteLine(n);

And the output was the correct, 996 come at first.

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Web Developer

Answer 3

Hi Matt,

The field you are ordering on probably is a string field, right? In string representation, 8 precedes 9, so 844569654 precedes 91. There are several things you can do:

• Treat the numbers as numbers, not as strings
• Pad all the numbers on the left hand side with zeros until they have the same length

Hope this helps

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Please mark the best replies as answers - Twitter: @rickvdbosch - Blog: http://bloggingabout.net/blogs/rick

Answer 4

Do what Rick tell you, like this

            var cdbips = from cdb in CDBs
                         join ip in IPs
                         on cdb.Cdbno equals ip.Cdbno
                         where cdb.Country == "Italy"
                         orderby Convert.ToInt32(cdb.Cdbno) ascending
                         select new classIP(cdb.Cdbno, ip.Ipno);

---

If you get your question answered, please come back and Mark As Answer.
Web Developer

Answer 5

I like your answers!!! The key was that I was doing an orderby on strings. Shame Microsoft doesn't give the flexibility to order string numbers. But I'm still gratefull as I'm using the free Express version at the moment.

cheers

Matt

Answer 6

I like your answers!!! The key was that I was doing an orderby on strings. Shame Microsoft doesn't give the flexibility to order string numbers. But I'm still gratefull as I'm using the free Express version at the moment.

It does, you just need to parse the strings into actual numbers before sorting on them.  If you didn't, then it would have no way of handling non-numeric strings.