```cs
Dictionary<int, List<int>> foo = GetFoo();
foreach (var (key, items) in foo)
{
    items = items.Where(item => item % 2 == 0); // unfortunately not in-place
    foo[key] = items; // unfortunately breaks iterator
}

```

I have a dictionary mapping keys to lists of ints `{ key: [ 1, 2, 3, ... ] }`

How can I filter the values of the dictionary? I want to get `{ key: [2, 4, ...] }` for example.