C# - Find all email addresses for an Active Directory user

I'm trying to get all the email addresses associated to a given AD user.

For the user I have the domain and the login name (ex. DOMAIN\UserName) and I the AD is storing the email addresses in:

1. The mail attribute.
2. In proxyAddresses attributes.

So far, I don't know what C# API to use to connect to the AD, and how to properly filter by the user to fetch all the email addresses. I'm using .NET 3.5.

Thank you.