Custom Database Functoid

Hi all,

I would like to create a custom functoid for my mapping needs that would
access a DB and return a DataTable (preferably) or at an Array of value. I
would have another functoid that would consume that Database functoid (and
the DataTable that it generates) and get a particular value out of it (based
on some other node value or loop index for example).
Those 2 functoids would work in concert, a bit like the "Table Looping" and
"Table Extractor" functoids work together.

Now in all the custom functoids example i see on the internet, functoids are
always of the type
public string DoSomething(string param1, string param2)
they ALWAYS manipulate string and returns string.

I have 2 questions:
1. Is there a limitation in the Type a functoid can use in his signature? If
yes, any reference to that?
2. Is there anyone who has or know of an example of more complex functoids
that use more complex datatypes? There is one in the Biztalk Samples
(%instal_dir%/SDK\Samples\XmlTools\CustomFunctoid) that uses an array
indirectly through a global variable but still all the functoids use only
string type as parameter and return type. But I am not really interested in
following that "global variable" road.

Thanks in advance,

Francois Malgreve