Linq Merge lists

Question

My class:

    public class Foo
    {
        public int A { get; set; }
        public List<Bar> Bars { get; set; }
    }

I've got IEnumerable<Foo>. I would like get List<Foo> grouping by A, and get Bars list, which contais all elements at Bars for group.

So final Foo.Bars should contains all elements of Bar at group

Is it possible with linq?

Aren't the Foos in your source IEnumerable<Foo> already that way? You source must be of a different type, right? What does the source actually look like? — bluevector
– bluevector, Commented Jun 15, 2012 at 13:12
No i would like get collection of the same type, but with merging lists — Andrew Kalashnikov
– Andrew Kalashnikov, Commented Jun 15, 2012 at 13:13

Tim Schmelter · Accepted Answer · 2012-06-15 13:32:39Z

5

var result = foos.GroupBy(f => f.A)
                 .SelectMany(grp => grp.Select(f => f.Bars));

As Rawling has mentioned, this returns not an IEnumerable<Foo>, so try this:

IEnumerable<Foo> result = 
            foos.GroupBy(f => f.A)
            .Select(grp => new Foo() { 
                A = grp.Key,
                Bars = grp.SelectMany(ff => ff.Bars).Distinct().ToList()
            });

I'm not sure whether you want a distinct list of Bars or not. Note that you may need to override Equals and GetHashCode in class Bar.

edited Jun 15, 2012 at 13:32

answered Jun 15, 2012 at 13:14

Tim Schmelter

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2 Comments

bluevector Over a year ago

This seems like what he might be looking for, but I'm still confused about the actual source.

Rawling Over a year ago

This won't return a List<Foo>.

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