How to Reference Filenames against SQL Data - Please Help

Question

Hi,
I'll explain a little...
1, I have a list of files invoices in pdf format (invoice filenames are the CustomerCode) that i want to send to the customer
2, I have a database with the customercode's and email address's.
3, I know how to do the mailing side of things but i do i make a match between the invoice filenames and the CustomerCode to Add that invoice as an attachment and send to the email address record that holds that account number?
 
Invoice files are held C:\billing\Invoices\*.pdf
And i have a linq to SQL Class with the Customer Table in which holds all the customercodes and email addresses.
I'd be so grateful if you could help me with this.
Thanks
Anthony