Question

Is it possible to replace the foreach loop below with linq?

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

List<Foo> fooList = GetFooList();
List<Bar> allBars = new List<Bar>();

foreach (Foo foo in fooList)
{
    allBars.AddRange(foo.Bars);
}

The closest I’ve gotten is:

var temp = fooList.Select(foo => foo.Bars).ToList();

which gives a List<List<Bar>>.

Answer 1

You can use SelectMany() on foo.Bars

allBars.AddRange(fooList.SelectMany(foo => foo.Bars));

If allBars variable does not contain anything before AddRange(), you could skip the object creation:

List<Bar> allBars = fooList.SelectMany(foo => foo.Bars).ToList();

And if you are not going to use fooList somewhere else, you could just write:

List<Bar> allBars = GetFooList().SelectMany(foo => foo.Bars).ToList();