We would like to make a note on the contacts how they signed up, and I am guessing the SourceName via the web interface is the appropriate field. However I cannot find anywhere in the api to fill it in.
This will be a free form field like it appears is available via the web interface for a contact.
Please direct me to where I can find it. We are using the C# wrapper.
The source name is automatically assigned for contacts based on your API Key, and this is done on the back-end of the API. As such it is not a field that can be freely set when creating or modifying contacts.
The best way to make a note on a contact is to use a custom field to store that data. In the V2 API custom fields are limited to a fixed set, and you can read a bit more about that here: http://developer.constantcontact.com/docs/contacts-api/api-gui-func.html
Please let me know if you have any questions!