public interface ICrudServiceIn this example, we have defined a generic interface ICrudService with a type parameter T representing the type of objects we want to fetch from the database or collection. We have also defined a class CustomerService that implements this interface for the Customer type. The GetAll method in CustomerService class will have the actual code that fetches all the customer records from the database or collection and returns them as a List{ List GetAll(); } public class CustomerService : ICrudService { public List GetAll() { // Code to fetch all customer records // and return as a List } }