Passing arrays to stored procedures

[William Garrison <postgres(at)mobydisk(dot)com>]

I have a stored procedure that takes a list of IDs and uses the ANY 
operator:

CREATE OR REPLACE FUNCTION CalculateTotals(
	customerList bytea[],
	out total bigint,
	out most_recent_login_date date)
AS $$
BEGIN
	SELECT
		SUM(totalsize), MAX(last_login)
	INTO
		$2,$3
	FROM
		customer
	WHERE
		customerid = ANY($1);
END;
$$ LANGUAGE 'plpgsql' STABLE;


I'm using npgsql and C#, and I've realized it doesn't support passing 
arrays.  Barring things like updating npgsql, what form of hackiness 
would work best here?

The customerIDs are GUIDs represented as 16-byte arrays.  I can pass 
them as encoded strings separated by commas or some such silliness.  But 
I don't see a nice clean split() function that returns me an array. :-(

I'm trying to find some way to pass a postgres array constructor syntax 
and have that evaluated, like ARRAY['binary':bytea,...,...] or 
{...,...,...} something like that.

Does anyone have any suggestions?