Why do I have to call base.OnAuthorization(filterContext)

[MATRIX^2]

I've seen plenty of guides where implementation of custom authorization filter involves calling base.OnAuthorization(filterContext) as final step. I have my own custom authorization filter and it works perfectly without above mentioned. However, when I add call to base.OnAuthorization(filterContext), my WebAPI service returns 401, even though all checks passed successfully. 1) Why do I have to call base.OnAuthorization?2) How come it returns 401 on it's own?EDIT: I'm thinking it has to do with default Membership and Role providers. Since I'm sort of skipping those, could that be the reason?As soon as I call base.OnAuthorization, my Response becomes 401.