02 | Beginning Code First Adam Tuliper | Technical Evangelist Christopher Harrison | Content Developer

Code First Simple Code First Creating classes Creating Data Context Initializing the database

Simple Code First

public class Artist { public int ArtistID { get; set; } public string Name { get; set; } public string Bio { get; set; } }

Code first classes… are just classes

Code first class design tips Just design your classes the way you typically would (for the most part) Use best practices ID for the ID You can still control the database Attributes Fluent API

Creating classes

But what about my database? Code First often does the right thing But it does need a little guidance For example, strings become nvarchar(max)

Basic database control Data annotations can be used to provide additional context System.ComponentModel.DataAnnotations https://msdn.microsoft.com/en- us/library/system.componentmodel.dataannotations(v=vs.110).aspx Not specific to Entity Framework Used by several other platforms, including MVC

Code First conventions Tables are automatically pluralized Tables are created in the dbo schema ID property is created as the primary key Identity or auto-count column

Table creation TableAttribute Schema Name ColumnAttribute

Strings Nullable nvarchar(max) is the default Attributes StringLengthAttribute MaximumLength MinimumLength RequiredAttribute

Numbers SQL data type is mapped to .NET data type RangeAttribute long becomes BigInt RangeAttribute Maximum Minimum

Numbers and nullability Numbers are value types in .NET .NET property must be marked as nullable Nullable<T> type?

Attributes and database control

Creating the Data Context

Creating the Data Context Just like creating a normal class It's like it's called Code First  public class MusicStoreDbContext : DbContext { public DbSet<Artist> Artists { get; set; } }

Creating the DbContext

The Find() method Regardless of the data type you're going to need to look the object up by its key Rewriting that code over and over again becomes tedious The Find method will do that for you Accepts a parameter that maps to the key Returns the object if it's found Returns null if it isn't

Creating a repository

Initializing the database

Testing requires a known starting state Entity Framework provides database initializers to create that state Create a class that inherits from the appropriate option CreateDatabaseIfNotExists DropCreateDatabaseWhenModelChanges DropCreateDatabaseAlways Override the Seed method to create database content Register the method with Database.SetInitializer

Initializing the database