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02 | Beginning Code First

Adam Tuliper | Technical EvangelistChristopher Harrison | Content Developer

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

Code First

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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 standard conventions– ID for the ID

• You can still control the database– Attributes– Fluent API

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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.compone

ntmodel.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– Name

Strings• Nullable nvarchar(max) is the default

• Attributes– StringLengthAttribute• MaximumLength• MinimumLength

– RequiredAttribute

Numbers• SQL data type is mapped to .NET data type– long becomes BigInt

• RangeAttribute–Maximum–Minimum

Value types and nullability• Dates and numbers are value types in .NET

• Value type properties must be marked as nullable– Nullable<T>– type?

DEMOAttributes and database control(warning... This demo is going to fail. Well, sort of.)

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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; }}

DEMOCreating 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

DEMOCreating a repository

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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

DEMOInitializing the database

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