Separating entity classes from EDMXĪgain, in an enterprise level application where separation of concerns is of great importance you certainly want to have your domain logic and your data access logic in separate projects. By default all generated code including the model classes for the Department and Employee entities sits in the same project. Once the wizard has completed the model is added to your project and you are able to view it in the EF Designer. The wizard lets you connect to the database and select the Department and Employee tables to be included in the model. Choose the “Generate from database” option in the Entity Data Model wizard. Start by creating a new class library project ( Mm.DataAccessLayer) and add a new ADO.NET Entity Data Model to it. Any user interface code should only communicate with the service or business layer and don’t have any references to the DAL.ġ. It is the only layer in the application that will actually know anything about and have any dependencies on EF. The DAL is simply a C# class library project where you define the model generated from the existing database along with the generic implementation for reading and modifying the data in the database. On top of this there may be some repositories to communicate with the DAL, a business layer containing logic and classes representing the business domain, a service layer to expose the business layer to clients and finally some user interface application such as a WPF desktop application or an ASP.NET web application. ()Ī large enterprise application will typically have one or more databases to store data and on top of this a data access layer (DAL) to access the database(s). PRIMARY KEY CLUSTERED ( ASC),ĬONSTRAINT FOREIGN KEY () There is a one-to-many relationship between the Department and Employee tables meaning an employee belongs to a single department and a department can have several employees. The database used in this example is a very simple one containing only the two tables listed below. There is a walkthrough on how you can create a local service-based database in Visual Studio 2012 available on MSDN here. Typically when you are doing database first development using EF you are targeting an already existing database but for testing and demo purposes you may of course generate a new one from scratch. As databases within enterprise environments are generally designed and maintained by database administrators (DBAs) rather than developers, this post will use the database first option where the EDM becomes a virtual reflection of a database or a subset of it. With both the model first and code first approaches the presumption is that you don’t have an existing database when you start developing the application and a database schema is created based on the model. It is an object-relational mapping framework (ORM) that enables developers to work with relational data using domain-specific objects without having to write code to access data from a database.ĮF provides three options for creating the conceptual model of your domain entities, also known as the entity data model (EDM) database first, model first and code first. This post is about how you can develop a generic data access layer (DAL) with full CRUD (Create, Read, Update and Delete) support using Entity Framework 5 with plain old CLR objects (POCOs) and short-lived contexts in a disconnected and stateless N-tier application.Įntity Framework (EF) is Microsoft’s recommended data access technology when building new. NET, C#, Entity Framework, N-tier | 159 Comments
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