public interface IEntityBase { int Id { get; set; } DateTime CreatedDate { get; set; } DateTime? UpdatedDate { get; set; } }The above code declares IEntityBase interface with three properties of `int` and `DateTime` type for `Id` and `CreatedDate` respectively. The `UpdatedDate` property can be set to null. This interface can be used as the base for other entity classes, allowing for consistent implementation across the domain model. The package library for IEntityBase could be Entity Framework Core, which is a popular C# ORM (Object-Relational Mapping) library. It provides functionalities for mapping database tables to C# classes and vice versa, making it easier to work with databases in .NET applications. IEntityBase could be used with Entity Framework Core to establish a standard for all classes that interact with the database.