c# - Type error trying to call Any() using Expression<Func<..>> from method -

i creating reusable mapping expression ef entity bll entity:

private expression<func<person, bool>> getnamefilter(string name) {     return person => person.profile.username == name; }  internal expression<func<ef.perk, bll.perk>> mapperkperk(string name) {     return perk => new bll.perk         {             id = perk.perkid,             name = perk.perkname,             description = perk.perkdescription,              //compilation error             owned = perk.players.any(getnamefilter(name))          }; } 

and getting compilation error on noted line. error reads:

icollection not contain definition 'any' , best extension method overload 'queryable.any(iqueryable, expression>)' requires receiver of type 'iqueryable'

but not happen when push expression in directly:

internal expression<func<ef.perk, bll.perk>> mapperkperk(string name) {     return perk => new bll.perk         {             id = perk.perkid,             name = perk.perkname,             description = perk.perkdescription,              //no compilation error             owned = perk.players.any(person => person.profile.username == name)         }; } 

why happening? type of both expressions same.

using linqexpression solution found below, getting following error @ runtime:

an exception of type 'system.invalidcastexception' occurred in linqkit.dll not handled in user code

additional information: unable cast object of type 'system.linq.expressions.instancemethodcallexpressionn' type 'system.linq.expressions.lambdaexpression'.

internal futurequery<perk> getplayerinfoperks(string username) {     return master             .perks             .visibleperks             .select(master.perks.mapperkperk(username))             .future(); } 

is due use of entityframework.future library?

why happening? type of both expressions same.

the type of both expressions not same - visually same. following valid:

dbcontext.persons.any(getnamefilter(name)) 

and not:

perk.players.any(getnamefilter(name)) 

why? because first expects expression<func<...>> while second - func<..> (the typical difference between iqueryable<t> , ienumerable<t> methods same name). hope see difference. when type directly, c# compiler magic emit 1 or another, when manually, supposed use correct one.

the problem addressed linqkit package invoke / expand custom extension methods (and more asexpandable).

for concrete example, linqkit solution this:

using linqkit;  ...  internal expression<func<ef.perk, bll.perk>> mapperkperk(string name) {     // linqkit requires expressions in variables     var namefilter = getnamefilter(name);     return linq.expr((ef.perk perk) => new bll.perk     {         id = perk.perkid,         name = perk.perkname,         description = perk.perkdescription,         owned = perk.players.any(p => namefilter.invoke(p))      }).expand(); }