public interface IUserRepository { void AddUser(User user); void UpdateUser(User user); void DeleteUser(User user); User GetUserById(int id); IEnumerableIn this interface, we define methods to add, update, delete, and retrieve users. We can also retrieve all users by using the GetAllUsers() method. This interface is typically used in conjunction with a concrete implementation of the repository, which is responsible for actually performing the CRUD operations on the data store. Therefore, the package library for the IUserRepository interface would likely be a data access or persistence library such as Entity Framework, NHibernate or Dapper.GetAllUsers(); }