Aggregate multiple arrays into one array (Linq)

Question

I'm having trouble aggregating multiple arrays into one "big array", I think this should be possible in Linq but I can't get my head around it :(

consider some method which returns an array of some dummyObjects

public class DummyObjectReceiver 
{
  public DummyObject[] GetDummyObjects  { -snip- }
}

now somewhere I have this:

public class Temp
{
  public List<DummyObjectReceiver> { get; set; }

  public DummyObject[] GetAllDummyObjects ()
  {
    //here's where I'm struggling (in linq) - no problem doing it using foreach'es... ;)
  }
}

hope it's somewhat clear what I'm trying to achieve (as extra I want to order this array by an int value the DummyObject has... - but the orderby should be no problem,... I hope ;)

I think I just answered this very question: stackoverflow.com/questions/780867 — Matt Hamilton
– Matt Hamilton, Commented Apr 23, 2009 at 10:23
Yes, it's the same principle, but this one has the added twist of having a list of objects with a method that returns the arrays. — Guffa
– Guffa, Commented Apr 23, 2009 at 11:18

Guffa · Accepted Answer · 2009-04-23 11:08:36Z

16

You use the SelectMany method to flatten the list of array returning objects into an array.

public class DummyObject {
    public string Name;
    public int Value;
}

public class DummyObjectReceiver  {

    public DummyObject[] GetDummyObjects()  {
        return new DummyObject[] {
            new DummyObject() { Name = "a", Value = 1 },
            new DummyObject() { Name = "b", Value = 2 }
        };
    }

}

public class Temp {

    public List<DummyObjectReceiver> Receivers { get; set; }

    public DummyObject[] GetAllDummyObjects() {
        return Receivers.SelectMany(r => r.GetDummyObjects()).OrderBy(d => d.Value).ToArray();
    }

}

Example:

Temp temp = new Temp();
temp.Receivers = new List<DummyObjectReceiver>();
temp.Receivers.Add(new DummyObjectReceiver());
temp.Receivers.Add(new DummyObjectReceiver());
temp.Receivers.Add(new DummyObjectReceiver());

DummyObject[] result = temp.GetAllDummyObjects();

answered Apr 23, 2009 at 11:08

Guffa

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2 Comments

AnthonyWJones Over a year ago

+1. I missed the "multiple" aspect in my now deleted answer.

Bluenuance Over a year ago

exactly what I was looking for :) extra thanks for including orderby! (still can only +1)

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