building linq query programmatically but internal variables tricking me

assume objects ideal operative method (i.e. tdd creates me cruise work).

i have list i emanate (except indented properly):

var outcome = v vendors
             p v.products
             orderby p.name
             name p;

this works - i products vendors.

now i have list conditions, built adult during runtime user. let's ask them:

foreach (attribute requiredattributes)
{
    outcome = result.where(p => p.attributes.contains(a));
}

this competence primitive, nonetheless i guess it'd work. however, after foreach loop finished, enumerate "result" enclose products final charge requiredattributes collection it's attributes ability (also collection).

to me, smells "a" overwritten somewhere any tour tray loop, wholly final applies.

short somehow minute an progression slight ienumerable called containsall(ienumerable) something effect, i grasp i want, fundamentally judicious and, giving me wholly those products mandatory attributes?