myDbSet.Select(x => new MyClass
            {
                IsSelected = x.ChildList.Any()
            })

myDbSet.Select(x => new
            {
                Item = x
                IsSelected = x.ChildList.Any()
            })

myDbSet.Select(anonymousTransformedExpression).ToList().
       .Select(newGeneratedExpression)

myDbSet.Select(x => new
            {
                x.Item.IsSelected = x.IsSelected
                return x.Item;
            })