Linq grouping with child condition

Question

I have ORM data type like below

public class PackData
{
   public int PackId
   public int ClientId
   public DateTime DateCreated
   public List<PackItemData> PackItems
}

public class PackItemData
{
   public int PackId
   public string DeviceId
}

I can query PackData and PackItemData with Linq

var data = DataTable.Where(pack =>  pack.DateCreated >= startDate 
                                    && pack.DateCreated <= endDate)

I want to group/distinct child data (PackItemData) to get unique result for device Id

How can I achieve that?

it might be helpful if you show a sample input and expected output — Selman Genç, Apr 01 '14 at 12:35
I expected output, List that all List already distinct for all, so I have device Id unique for all List thats mean, List only have one for specific deviceId — navirius, Apr 02 '14 at 03:21

Aducci · Answer 1 · 2014-04-01T12:53:10.607

0

I think you are looking for SelectMany. This will flatten out your List<List<PackItemData>> to List<PackItemData>

var data=DataTable.Where(pack =>  pack.DateCreated >= startDate 
                                  && pack.DateCreated <= endDate)
                   .SelectMany(i => i.PackItems)
                   .GroupBy(i => i.DeviceId).Select(i => i.First());

edited Apr 01 '14 at 12:53

answered Apr 01 '14 at 12:39

Aducci

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But what will be the output of this query?? He wanted to group items ryt?? This query will provide only the distinct deviceids.. – Arun Aravind Apr 01 '14 at 12:43
This query give me a PackItems result data, how can I get PackData list result that pack items already distinct by device Id for all pack datas? – navirius Apr 02 '14 at 03:13

score 0 · Answer 2 · answered Apr 01 '14 at 12:42

var groups = DataTable
    .Where(pack => pack.DateCreated >= startDate && pack.DateCreated <= endDate)
    .SelectMany(pack => pack.PackItems)
    .GroupBy(item => item.DeviceId);

You might want to start with SelectMany which will allow you to enumerate over all of the PackItems in all of the PackDatas. This gives you an IEnumerable<PackItemData> which you can then use in your grouping.

score 0 · Answer 3 · edited May 23 '17 at 12:05

0

Linq GroupBy and Distinct methods should get you what you need.

var data=DataTable.Where(pack => pack.DateCreated >= startDate && pack.DateCreated <= endDate)
                  .Select( pack => pack.PackItems)
                  .GroupBy( p => p.PackId, p => p.DeviceId, (key, p) => new PackItemData { PackId = key, DeviceId = p});

I'm not 100% this works, as I have yet to run a test, but this should get you close to where you're going.

Source: Group by in LINQ

edited May 23 '17 at 12:05

Community

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answered Apr 01 '14 at 12:43

CodeMonkey1313

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Use SelectMany Instead. – Arun Aravind Apr 01 '14 at 12:50

score 0 · Answer 4 · answered Apr 01 '14 at 12:52

0

 var data = DataTable.Where(pack =>  pack.DateCreated >= startDate 
                              && pack.DateCreated <= endDate).SelectMany(s=> s.PackItems).GroupBy(p => p.DeviceId).Select(r=> r);

I think this should work.

answered Apr 01 '14 at 12:52

Humayoun Kabir

275
1
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This query give me a PackItems result data, how can I get PackData list result that pack items already distinct by device Id for all pack datas – navirius Apr 02 '14 at 03:13

Linq grouping with child condition

4 Answers4