Linq GroupBy into new object

Question

First of all I am new to Linq.

I have a list of objects named Lba that have different properties to be grouped by. My object properties are :

int aId, int bId, int max, int min, CustomObject1? Co1, CustomObject2? Co2, CustomObject3? Co3

I want to group my objects into a new object LbaGroup that have the following properties

int aId, int bId, int max, int min, IList<CustomObject1> Co1, IList<CustomObject2> Co2, IList<CustomObject3> Co3

I grouped my objects with the following query but it returns a List>

var query = myLbaList .GroupBy(a => new {a.aId, a.bId, a.max, a.min}) .Select(a => a.ToList()) .ToList();

I am able to build my new objects with 2 foreach loops but I was wondering if there is a direct way to achieve that with Linq.

Thank you.

Edit: My loops look like :

foreach(List<Lba> LbaList in query){ LbaGroup myNewObject = new LbaGroup{ Co1 = new List<CustomObject1>(), Co2 = new List<CustomObject2>(), Co3 = new List<CustomObject3>(), } foreach(Lba oldObject in LbaList){ myNewObject.aId = oldObject.aId; myNewObject.bId = oldObject.bId; myNewObject.max = oldObject.min; if oldObject.Co1 != null myNewObject.Co1.Add(oldObject.Co1); if oldObject.Co2 != null myNewObject.Co2.Add(oldObject.Co2); if oldObject.Co3 != null myNewObject.Co3.Add(oldObject.Co3); } }

Hi, can you show the loops as well?

Stefan
– Stefan

2018-12-05 10:06:29 +00:00
Commented Dec 5, 2018 at 10:06 — Stefan
– Stefan, Commented Dec 5, 2018 at 10:06

Dmitrii Bychenko · Accepted Answer · 2018-12-05 10:13:13Z

Something like this:

var result = myLbaList .GroupBy( a => new {a.aId, a.bId, a.max, a.min}, // Key a => new {a.Col1, a.Col2, a.Col3}) // Values .Select(chunk => new { // From Key aId = chunk.Key.aId, bId = chunk.Key.bId, max = chunk.Key.max, min = chunk.Key.min, // From Values Col1 = chunk .Where(item => item.Col1.HasValue) // not null items .Select(item => item.Col1.Value) // CustomObject1? to CustomObject1 .ToList(), Col2 = chunk .Where(item => item.Col2.HasValue) .Select(item => item.Col2.Value) .ToList(), Col3 = chunk .Where(item => item.Col3.HasValue) .Select(item => item.Col3.Value) .ToList(), }) .ToList();

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