LINQ - Getting all child records from all parents

Question

I have two models:

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

class Bar
{
    public int Value { get; set; }    
}

Having an instance of List<Foo>, how can I get all Value using a LINQ query?

Thank you all

Answer 1

SelectMany is normally the way to flatten hierarchies, so:

var values = myList.SelectMany(foo => foo.Bar)
                   .Select(bar => bar.Value);

The SelectMany will give you an IEnumerable<Bar>, and then the Select projects that sequence of Bar objects to the Value property of each, returning an IEnumerable<int>.

As a query expression, this would be:

var values = from foo in myList
             from bar in foo.Bar
             select bar.Value;