I want to access all the contacts and mailing list in C# code Is there any way this can be achieved
Outbound E-mail functionality is not exposed by the Core Service.
However, Audience Manager / Outbound E-mail does have its own C# management API that you can use on the server (Tridion.AudienceManagement.API).
If you need to call it from another machine, I'm afraid you will have to create your own web service that calls the API. There is a web service available, but it does not yet expose everything you need (only import/export functionality for Contacts)