Update your contacts in MailChimp to reflect a contact list from another source, for example a membership database.
The library is a wrapper for Brandon Seydel's MailChimp.Net project and supports tagging contacts and populating both the in-built merge fields (first name, last name, etc.) and custom merge fields that you've previously added in MailChimp.
For examples of how to use this library, see MailChimpSyncerExampleApp/Program.cs.