LINQ help, group by of set of items in an object

Here's my 2 classes

public class Item
{
    public string Path { get; set; }
    public List<Sub> Subs { get; set; }
}

public class Sub
{
    public string Name { get; set; }
}

private void Test()
{
    Sub sub1 = new Sub() { Name = "SUB1" };
    Sub sub2 = new Sub() { Name = "SUB2" };
    Sub sub3 = new Sub() { Name = "SUB3" };

    Item item1 = new Item() { Path = "开发者_如何学编程/Path1" };
    Item item2 = new Item() { Path = "/Path2" };
    Item item3 = new Item() { Path = "/Path3" };

    item1.Subs.Add(sub1);
    item1.Subs.Add(sub2);

    item2.Subs.Add(sub1);
    item2.Subs.Add(sub3);

    item3.Subs.Add(sub1);
    item3.Subs.Add(sub2);
    item3.Subs.Add(sub3);

    List<Item> items = new List<Item>();
    items.Add(item1);
    items.Add(item2);
    items.Add(item3);
}

I want a grouped collection that looks something like this

sub1 -> item1, item2, item3

sub2 -> item1, item3

sub3 -> item2, item3

How can I accomplish this?

Thanks much!

---

I'm assuming item1, item2, item3 are part of a new List<Item> whose name is items

//List<Item> items = new List<Item>();
//items.Add(item1);
//items.Add(item2);
//items.Add(item3);

var groupedBySub = from item in items
                   from s in item.Subs
                   group item by s into g
                   select new{ Sug = g.Key, Items = g };

---

Something like this i v4.0?

new[]{ item1, item2 ,item3 }
   .SelectMany(i => i.Subs,(i,s)=>new { Sub=s,Item=i })
   .ToLookup(l=>l.Sub,l=>l.Item)

I dont know if that'll work in 3.5 though

---

This is one way:

var items = new[] {item1, item2, item3};

        var result = from s in items.SelectMany((i, index) => i.Subs)
                     group s by s.Name
                     into g
                     select new {
                       Sub = g.Key,
                       Items = items
                          .Where(i => i.Subs.Any(s => s.Name == g.Key))
                          .Select(i => i)
                          .ToList()
                     };