The DAL (data access layer) is the core layer that interacts with the backend database. There are certain core classes we develop, which communicates with the database, manage connections and execute the CRUD operations. Certain patterns can be implemented to minimize the redundant effort of opening and closing connections and applying transactions that can be encapsulated through a simple interface and used by the business layer to perform CRUD operations. The most widely used pattern for this layer is the Repository pattern, which we will explore later in this chapter.