Is there a way to flatten a .Net ILookup into a List?

Question

Is there a quick way to get a flattened `List` from an `ILookup` that was created from the `IEnumerable` extension? Updated with example ``` List list = new List(); var lookup = list.ToLookup(key => key); list = lookup.?? // How to convert the lookup back to the list ```

Accepted Answer

```
lookup.SelectMany( x => x ).ToList()
```

The transformation to `ILookup` and back again will have most likely changed the order, however.

Is there a way to flatten a .Net ILookup<TKey, TElement> into a List<TElement>?

Solution

Problem