SelectMany Three Levels Deep

Question

I can flatten the results of a child collection within a collection with SelectMany:

 // a list of Foos, a Foo contains a List of Bars
 var source = new List<         


        

Answer 1

var q = (
    from f in foo
    from b in f.Bars
    from w in b.Widgets
    select w.WidgetId
   ).ToList();

Also note that if you want the unique list, you can do .Distinct().ToList() instead.