Database First Approach

This is another way of creating model classes and work with them. In this workflow model, it supports:

• Creates Model / POCO objects from an existing database and these will become the link between the database and controller(s)
• It uses the model/database sync, code generation, in the same way as we used in the Model First approach
• This is an alternative approach provided by Entity Framework besides Code First and Model First approaches

Database First approach is recommended when:

• Working with stable databases schemas
• Changes to database and models are incremental
• When you have a database designed separately by DBAs or if you have existing database

Advantages

• Useful when the database is already existing
• Simple to create the data model using existing database objects
• Mapping and creation of keys and relationships are automatically handled by EF and no need to write any code
• Usually preferred for intense data and large applications
• Easy to avoid data loss on changes as you wlll work from database perspective
• Query performance and better integrated with Stored Procedures and Functions

Disadvantages

• Giant pile of auto generated code when working with an huge database to generate EDMX
• Always needs to extend the auto generated classes to extend the functionality
• Creating associations, foreign keys, constraints etc. from the database can be more difficult
• Not easy to sync database changes made locally
• Sometimes handling edmx with version controlling is challenge
• Database deployment is a painful process
• Going forward EF will not support EDMX based modeling

Steps to implement Database First approach

• Create a new ASP.NET MVC or Web API project
• Using Manage Nuget Packages option install latest Entity Framework
• Update web.config with connection string
• Generate Model(s) by
  • Data -> ADO.NET Entity Data Model
  • Then pick "EF Designer" from Database
  • Pick newly created context from web.config as new context class name
  • Select needed SQL objects like Tables, Views and Stored Procedures
  • Once clicking on Ok, Models and .edmx will be generated after theses steps
• Updating .edmx can be done by
  • Make required changes using SSMS
  • From .edmx, right click and pick "Update Model from Database" option
• Fluent API will go hand to hand to create relationships like one-to-zeroorone, one-to-many and many-to-many etc.