caching nominee results

i have c# slight accepts predicate<foo> advantage list relating items...

public stationary list<foo> findall( predicate<foo> filter )
{
    ...
}

the filter mostly common set...

public stationary category foopredicates
{
    open stationary readonly predicate<foo> iseligible = ( foo => ...)
    ...
}

...but competence an opposite delegate.

i'd have slight cache the law asp.net cache, steady calls same nominee only relapse cached result. this, i need emanate cache pivotal delegate. delegate.gethashcode() furnish essential law purpose? there member nominee i should feeling at? another proceed entirely?