c# - How do I get a distinct list of list types -

this code (copy , paste linqpad if like)

var messageusers = new [] {      new { msgid = 2, userid = 7 },     new { msgid = 2, userid = 8 },     new { msgid = 3, userid = 7 },     new { msgid = 3, userid = 8 },     new { msgid = 1, userid = 7 },     new { msgid = 1, userid = 8 },     new { msgid = 1, userid = 9 }};  messageusers     .groupby (x => x.msgid, x => x.userid)     .select (x => x.select (y => y))     .distinct()     .dump(); 

the results {7,8}, {7,8}, {7,8,9}

what want {7,8}, {7,8,9}.

basically want remove duplicate lists. haven't tried think achieve creating comparer , passing distinct method. use in linq entities query without bringing thousands of rows client isn't option.

for clarification...i need return list> contents of each inner list distinct in comparison of other inner list.

the problem .distinct() determines what's distinct based on gethashcode() , equals() implementation of underlying objects. in case, underlying object implements ienumerable<>, uses default object implementation methods--which based purely on whether objects occupy same space in memory. far can tell, sequences not distinct, though have same values in them.

how this?

messageusers     .groupby (x => x.msgid, x => x.userid)     .groupby(x => string.join(",", x))     .select(x => x.firstordefault())     .dump(); 

the idea group key represents combined value of elements in list. pass custom iequalitycomparer<> distinct method in original code, seems fair bit of effort trivial.

it's worth noting won't work if you're using linq entities or that.

update

to make list<list<int>>, you'll need few .tolist()s thrown in there:

messageusers     .groupby (x => x.msgid, x => x.userid)     .groupby(x => string.join(",", x))     .select(x => x.firstordefault().tolist())     .tolist()     .dump(); 

but i'm frankly not sure why matters you.