LINQ Convert Dictionary to Lookup

Question

I have a variable of type Dictionary>
I want to convert it to a Lookup.

<

Answer 1

How about:

var lookup = dictionary.SelectMany(pair => pair.Value,
                                   (pair, Value) => new { pair.Key, Value })
                       .ToLookup(pair => pair.Key, pair => pair.Value);

It does feel like a little bit of a waste doing this when the dictionary already has all the information grouped appropriately, but I can't see a simple way round that. Of course you could implement ILookup yourself with a wrapper around the dictionary...