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 = source.SelectMany(foo => foo.Bar)
          .SelectMany(bar => bar.Widget,(bar,widget) => widget.WidgetId)
          .ToList();

we can call this overload of SelectMany() with allow us to specify the projection using lambda experession