Question

I have two object models that looks like this:

public class MyObject
{
   public List<SomeOtherObject> TheListOfSomeOtherObjects { get; set; }
}

public class SomeOtherObject
{
   long SomeOtherObjectID { get; set; }
}

And I have a list of MyObjects called ListOfMyObjects from which I want to extract all the SomeOtherObjectID that are inside lists TheListOfSomeOtherObjects

I want to write something like this:

var ListOfAllSomeOtherObjectID = (from l in ListOfMyObjects
                           select l.SomeOtherObject.SomeOtherObjectID ).ToList();

It’s not working because of the syntax. How do I get a list of the nested lists?

Thanks for your suggestions.

Answer 1

You’re trying to flatten the nested lists:

var allChildren = myObjects.SelectMany(o => o.ChildObjects).ToList();

If you then want to get a property of those objects, you’ll need a separate Select() call:

var allChildren = myObjects.SelectMany(o => o.ChildObjects)
                           .Select(c => c.SomeProperty)
                           .ToList();