Linq extension method, how to find child in collection recursive

Question

I\'m already familiar with Linq but have little understanding of extension methods I\'m hoping someone can help me out.

So I have this hierarchical collection pseudo cod

Answer 1

I'm just refactoring dtb's solution to make it more generic. Try this Extension method:

public static IEnumerable Flatten(this IEnumerable source, Func recursion) where R : IEnumerable
{
    return source.SelectMany(x => (recursion(x) != null && recursion(x).Any()) ? recursion(x).Flatten(recursion) : null)
                 .Where(x => x != null);
}

And you can use it like this:

productList.Flatten(x => x.Children).Where(x => x.ID == id);