Identification of serial fields

Hello:

I continue to be working in my .NET Data provider for postgres 7.4, i
want to know if there are a simple way for identify autoincrement
fields, i see that for serial and big serial fields the default value is
'nextval(...)' this can be a way for know it but i want to know if there
are a better way :)

Thanks in advance.

--
Best regards

Carlos Guzmán Álvarez
Vigo-Spain