What is the difference between code first and database first

Question

What is the difference between code first and database first technology?

Soumalya Das · Answer

The ADO.NET Entity Framework allows developers to choose any one approach among three possible approaches: Database First Model First and Code First. Database First: It is a more data-centric design that is based on an existing database. The Entity Framework is able to generate a business model based on the tables and columns in a relational database. The information about our database structure (store schema) our data model (conceptual model) and the mapping among them is stored in XML in an .edmx file. Model First: In this approach we don't have an existing database and the Entity Framework offers a designer that can create a conceptual data model. It also uses an .edmx file to store the model and mapping information. When the model has been created then the Entity Framework designer can generate the database schema that can be used to create the database. Code First: Whether you have an existing database or not you can code your own classes and properties that correspond to tables and columns and use them with Entity Framework without an .edmx file. In this approach Entity Framework does not leverage any kind of configuration file (.edmx file) to store the database schema because the mapping API uses these conventions to generate the database schema dynamically at runtime.

Nilesh Sawardekar · Answer

Code first Very popular because hardcore programmers don't like any kind of designers and defining mapping in EDMX xml is too complex. Full control over the code (no autogenerated code which is hard to modify). General expectation is that you do not bother with DB. DB is just a storage with no logic. EF will handle creation and you don't want to know how it does the job. Manual changes to database will be most probably lost because your code defines the database. Database first Very popular if you have DB designed by DBAs developed separately or if you have existing DB. You will let EF create entities for you and after modification of mapping you will generate POCO entities. If you want additional features in POCO entities you must either T4 modify template or use partial classes. Manual changes to the database are possible because the database defines your domain model. You can always update model from database (this feature works quite good). I often use this together VS Database projects (only Premium and Ultimate version).