c# - Concatenating three lists into one with LINQ throws an exception -

ok, must doing dumb, shouldn't work? have following 3 lists:

var commonviews = (from v in context.tpm_views v.viewid < 0 select v); // iqueryable<tpm_views> var ownedviews = (from v in context.tpm_views v.ownerid == userid && v.viewid > 0 select v); // iqueryable<tpm_views> var sharedviews = (from v in context.tpm_user.include("tpm_views2") v.userid == userid select v).first().tpm_views2; // entitycollection<tpm_views> 

each list has proper values , count. can return 1 of these lists:

return commonviews.tolist(); 

and can return two of these lists:

return commonviews.concat(ownedviews).tolist(); 

however, when try return three:

return commonviews.concat(ownedviews).concat(sharedviews).tolist(); 

i exception:

unable create constant value of type 'entity.tpm_views'. primitive types or enumeration types supported in context.

what doing wrong? 3 values indeed enumerable. mostly, i'm asking question because it's best possible way guarantee i'll notice problem 30 seconds after posting.

update:

i'm 93% sure problem here:

var sharedviews = (from v in context.tpm_user.include("tpm_views2") v.userid == userid select v).first().tpm_views2; 

this looks enumerable list of tpm_views object, , can call tolist() on , correct data, doesn't play other lists.

update 2:

this works. points person can tell me why!

commonviews.tolist().concat(ownedviews.tolist()).concat(sharedviews.tolist()).tolist(); 

the problem concat() on ef iqueryable<t> turn entire concatenation single query.

when call .concat(sharedviews), you're passing scalar (pre-loaded) collection of nested entity class.
ef doesn't know how convert query, complains.

you can make faster calling asenumerable() instead of tolist().