Update:
If you are using Entity Framework Core you should use the following syntax
var hierarchy = from p in ctx.Parents
.Include(p => p.Children)
.ThenInclude(c => c.GrandChild)
select p;
Update:
If you are using Entity Framework Core you should use the following syntax
var hierarchy = from p in ctx.Parents
.Include(p => p.Children)
.ThenInclude(c => c.GrandChild)
select p;