How can I find object in List with Linq?

Question

I have a object:

public class MyObject 
    {
        public int Id { get; set; }     
        public List<MyObject> Items { get; set; }     
    }

And I have list of MyObject:

List<MyObject> collection = new List<MyObject>();

collection.Add(new MyObject()
{
     Id = 1,
     Items = null 
});

collection.Add(new MyObject()
{
     Id = 2,
     Items = null
});

collection.Add(new MyObject()
{
     Id = 3,
     Items = null
});


List<MyObject> collectionMyObject = new List<MyObject>();

collectionMyObject.Add(new MyObject()
{
     Id = 4,
     Items = collection
});

collectionMyObject.Add(new MyObject()
{
     Id = 5,
     Items = null
});

How can I find object with Id = 2 in collectionMyObject with Linq ?

Andrei · Accepted Answer · 2013-07-01 11:03:45Z

18

If you are trying to find an object in collectionMyObject which has item with id 2, then this should work:

MyObject myObject = collectionMyObject.FirstOrDefault(o => o.Items != null && o.Items.Any(io => io.Id == 2));

And if you are try to find an inner item with id 2, then this query with SelectMany might be helpful:

MyObject myObject1 = collectionMyObject.Where(o => o.Items != null).SelectMany(o => o.Items).FirstOrDefault(io => io.Id == 2);

edited Jul 1, 2013 at 11:03

answered Jul 1, 2013 at 9:40

Andrei

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1 Comment

Alexandr Over a year ago

Thanks for the answer! I'm a little corrected query and it works Where(s => s.Items != null).SelectMany(o => o.Items).FirstOrDefault(io => io.Id == 2);

orel · Accepted Answer · 2013-07-01 09:58:30Z

9

var item = collectionMyObject.FirstOrDefault(x => x.Id == 2);

EDIT: I misread the question so Andrei's answer looks better than mine.

edited Jul 1, 2013 at 9:58

answered Jul 1, 2013 at 9:38

orel

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1 Comment

Alexandr Over a year ago

Thanks for the answer! I probably asked the wrong question I had in mind, the search for Items too.

DGibbs · Accepted Answer · 2013-07-01 09:38:39Z

4

Simple:

var obj = collectionMyObject.FirstOrDefault(o => o.Id == 2);

answered Jul 1, 2013 at 9:38

DGibbs

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Comments

Sandy · Accepted Answer · 2013-07-01 10:16:33Z

1

Another way may be:

(from c in collection where c.Id == 2 select c).ToList;

It should give a list in return. If want a single entry, then replace ToList() with FirstOrDefault().

Hope it helps.

answered Jul 1, 2013 at 10:16

Sandy

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Comments

Belogix · Accepted Answer · 2013-07-01 09:38:00Z

0

Using the Where keyword and a lambda like so:

MyObject result = collectionMyObject.Where(x => x.Id == 2).FirstOrDefault()

Or, to find in the Items sub-collection simply do:

MyObject result = collectionMyObject.Where(x => x.Item.Id == 2).FirstOrDefault()

answered Jul 1, 2013 at 9:38

Belogix

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