This document provides an overview of managing databases using Entity Framework Core and Code First Migrations. It discusses using the Fluent API for mapping entity classes to database tables. Code First Migrations allows managing the development cycle between code and the database by generating scripts to synchronize schema changes. Migrations create snapshots of the database that allow migrating and scripting SQL changes between different points in development.

1. 04 | Managing the Database
Adam Tuliper | Technical Evangelist, Microsoft
Christopher Harrison | Content Developer, Microsoft

2. Module Overview
• Fluent API
• Code First Migrations

3. Fluent API

4. Data Annotations vs Fluent API
• Why use data annotations (attributes)?
– Simple, works well for basic scenarios
– Some like attributes where they affect properties
– Integrates with MVC validation
• Why use Fluent API?
– Keeps domain classes clean - configuration in separate section
– More supported operations (advanced mappings, datetime precision, fixed
length and non-Unicode strings, etc)
– Using view models for views? Use Fluent for domain entities
– Fluent API allows very readable method cascading
• builder.Entity<Album>().Property(t => t.Name).IsRequired().HasMaxLength(60);

5. Separate Fluent & Data Annotations
• EF recognizes subset
– StringLength
– Range
– Required
– MinLength
– MaxLength
• This works, but purists may have a problem
– Mixes persistence, presentation, and validation logic

6. Using Fluent API without Data Annotations?
• How would we validate then?
• We would
– Map view model to Entity
– Save Entity
– Catch DbEntityValidationException
– Add errors to ModelState
• See code comments

7. What does Fluent Api support?
• Easily remapping legacy names to code names
– Customer.Unique_ID Customer.CustomerId
– ShipInfo.Unique_ID to ShipInfo.ShipInfoId
• Single type to multiple tables, vice versa
• Schema mapping
• Mapping table per type, table per class, entity & table splitting
• keys, length, index

8. OnModelCreating
• Override OnModelCreating in DbContext
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.HasDefaultSchema("MusicStore");
modelBuilder.Entity<Album>()
.Property(e => e.Title)
.HasColumnName("Album_Title");
modelBuilder.Entity<Album>()
.HasRequired<Artist>(s => s.Artist)
.WithMany(s => s.Albums);
}

9. DEMODEMO
Fluent API Basics

10. Remapping legacy tables
• Often legacy databases use ‘bad’ naming conventions
• Fluent API allows mapping scenarios
– Any column name to any field
– Table per type - subclasses have their own table ex Animal, Cat, Dog
– Table per class
– Entity splitting – multiple entities per table
– Table Splitting- multiple tables per entity

11. DEMODEMO
Fluent API Remapping tables and columns

12. Code First Migrations

13. Traditional DB/Code Management
• We can manage databases for our apps in many ways
• Create code, write sql, create database
• Create database, write code, script database

14. DEMODEMO
Manual Script Management

15. What’s the problem?
• Keeping code and database in sync was issue
• Managing versions requires significant manual effort
• Typically ‘undo’ scripts aren’t created
• Ensuring app version matches database version
– Ever forget/lose a script?
• Fix issues (many ‘went to production’ bugs)
– string customer; didn’t validate to varchar(50)

16. What would help?
• Our apps run code that maps between database and code
– Definition of ORM
• We write code, would be nice to have feature to manage scripts
– This is where Code First applies

17. What are code first migrations?
• Provides a way to manage dev cycle between code & db
• Allows you to
– Create point in time snapshots as ‘migrations’
– Generate scripts to sync code and database
– Allows migrating & scripting SQL between various snapshots
– Including upgrading and downgrading
• Can this help for existing databases?
– Code or reverse engineer into models, add migration
– Add-Migration Initial –IgnoreChanges

18. How do Code First Migrations work?
• Code created under default Migrations folder
• Each new Migration (add-migration) adds new code
• Can overwrite/update existing migrations
– Add-migration AddedShipInfo
– Developer adds more properties to ShipInfo class
– Add-migration AddedShipInfo (updates existing migration)
• Push to database
– Update-database -script
• Can configure automatic migrations

19. DEMODEMO
Setting up migrations

20. DEMODEMO
Customizing Migrations

21. DEMODEMO
Managing an existing database

22. Resources
• Code first migrations in team environments
– https://msdn.microsoft.com/en-us/data/dn481501.aspx
• Configuring/Mapping Properties and Types with the Fluent API
– https://msdn.microsoft.com/en-us/data/jj591617.aspx

23. ©2014 Microsoft Corporation. All rights reserved. Microsoft, Windows, Office, Azure, System Center, Dynamics and other product names are or may be registered trademarks and/or trademarks in the
U.S. and/or other countries. The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft
must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after
the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.
©2014 Microsoft Corporation. All rights reserved. Microsoft, Windows, Office, Azure, System Center, Dynamics and other product names are or may be registered trademarks and/or trademarks in the
U.S. and/or other countries. The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft
must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after
the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.