.net - How to produce a fully unique lookup? -

let's have ienumerable of key/value pairs, contains duplicates. if call tolookup on , pass lambdas select key , value, i'll end lookup keys unique, lists of values can contain duplicates. there way end lookup none of lists of values contain duplicates, in single linq query statement?

i can't call distinct on original sequence because elements duplicates value not object identity, , distinct doesn't take lambda selector use.

you can use groupby before building lookup in combination select many. doesnt feel however:

something this:

sequence.groupby(kvp => _getkey(kvp))         .selectmany(grp => grp.distinct()                               .select(value => new { grp.key, value = value}))         .tolookup(grp => grp.key, grp=> grp.value); 

alternative using dictionary, since not quite sure why want use lookup.

sequence.groupby(kvp => _getkey(kvp))         .select(g => new { g.key, values = new hashset<whatever>(g)})         .todictionary(v => v.key, v => v.values); 

alternative hashset providing equalitycomparer distinct()

 public sealed class whatevercomparer : iequalitycomparer<whatever>  {     ... implement interface..  } 

then

sequence.groupby(kvp => _getkey(kvp))         .select(g => new { g.key, values = g.distinct(new whatevercomparer()).toarray()})         .todictionary(v => v.key, v => v.values);