Entity Framework Core

Angel Soto

dreamensys@gmail.com

@dreamensys

Full Stack Developer

Qué es EF?
Ventajas y desventajas?
Tipos de modelo(Code First vs Database first)
Cadenas de conexion
Migraciones
Constraints(Data annotations vs Fluent API)
Siembra de datos
Relacion entre tablas

Qué es EF

Entity Framework Core es una versión ligera, extensible y multiplataforma del mapeador objeto-relacional (ORM) de Microsoft, Entity Framework es la plataforma oficial de acceso a datos de Microsoft.

Ventajas

Facilidad
LINQ
Soporte procedimientos almacenados.
Mapeos
Table Splitting
Transacciones
Soporta proveedores como: SQL Server, MySQL y PostgreSQL entre otros.

Desventajas

Performance
Alto acoplamiento
Más lento que ADO.NET

Tipo de modelo

Cadenas de Conexión

"ConnectionStrings": {
    "DefaultConnection": "Server=(localdb)\\mssqllocaldb;Database=IntecapBooksTemplate;Trusted_Connection=True;MultipleActiveResultSets=true"
  },

Server
Database
Trusted_Connection
Otros más

Migraciones

public partial class AddPhoneNumber : Migration
{
    protected override void Up(MigrationBuilder migrationBuilder)
    {
        migrationBuilder.AddColumn<string>(
            name: "PhoneNumber",
            table: "Customers",
            nullable: true);
    }

    protected override void Down(MigrationBuilder migrationBuilder)
    {
        migrationBuilder.DropColumn(
            name: "PhoneNumber",
            table: "Customers");
    }
}

Relaciones entre tablas

public class Author
{
    public int AuthorId { get; set; }
    public string Name { get; set; }
    public AuthorBiography Biography { get; set; }
}
+-
public class AuthorBiography
{
    public int AuthorBiographyId { get; set; }
    public string Biography { get; set; }
    public int AuthorId { get; set; }
    public Author Author { get; set; }
}

1.Uno a uno

Relaciones entre tablas

public class Author
{
    public int AuthorId { get; set; }
    public string Name { get; set; }
    public List<Book> Books { get; set; }
}

public class Book
{
    public int BookId { get; set; }
    public string Title { get; set; }
    public int AuthorId { get; set; }
    public Author Author { get; set; }
}

2.Uno a muchos

Relaciones entre tablas

public class Book
{
    public int BookId { get; set; }
    public string Title { get; set; }
    public List<Category> Categories { get; set; }
}

public class Category
{
    public int CategoryId { get; set; }
    public string CategoryName { get; set; }
    public List<Book> Books { get; set; }
}

3.Muchos a muchos

Constraints

public class Blog
{
    public int BlogId { get; set; }
    [Required]
    public string Url { get; set; }
}

Data Annotations

class MyContext : DbContext
{
    public DbSet<Blog> Blogs { get; set; }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Blog>()
            .Property(b => b.Url)
            .IsRequired();
    }
}

Fluent API

los más usados...

Constraint	Ejemplo
Required
Key
ConcurrencyCheck
NotMapped
MaxLength

[Required]
public string Url { get; set; }

[Key]
public int OrderDetailID { get; set; }

[ConcurrencyCheck]
public string Version { get; set; }

[NotMapped]
public class BlogMetadata

[MaxLength(50)]
public string LastName { get; set; }

Constraint	Ejemplo
MinLength
StringLength
ForeignKey
Table
Column
RegularExpression

[MinLength(3)]
public string LastName { get; set; }

[StringLength(50)]
public string LastName { get; set; }

[ForeignKey("OrderID")]
public Order Order { get; set; }

[Table("UserInfo")]
public class Person

[Column("LName")]
public string LastName { get; set; }

entre otros...

[RegularExpression(@"^[a-zA-Z''-'\s]{1,40}$")]
public object LastName;

Constraints(Fluent API)

class MyContext : DbContext
{
    public DbSet<Blog> Blogs { get; set; }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Blog>()
            .Property(b => b.Url)
            .IsRequired();
    }
}

Siembra de datos

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    modelBuilder.Entity<Author>().HasData(
        new Author
        {
            AuthorId = 1,
            FirstName = "William",
            LastName = "Shakespeare"
        }
    );
    modelBuilder.Entity<Book>().HasData(
        new Book { BookId = 1, AuthorId = 1, Title = "Hamlet" },
        new Book { BookId = 2, AuthorId = 1, Title = "King Lear" },
        new Book { BookId = 3, AuthorId = 1, Title = "Othello" }
    );
}

Otros conceptos...

Lazy Loading
Explicit Loading
Eager loading
Tracking
N+1 problem