INTRODUCTION TO

ENTITY FRAMEWORK CORE

Content

  • What is Entity Framework Core

  • Why use Entity Framework Core

  • Entity Framework Latest Version

  • EF Core Development Approaches

  • EF Core Database Provider

  • DbContext

  • EF Core Model

Entity Framework Core?

An open-source ORM(object-relational mapping) framework for .NET applications supported by Microsoft

 

A lightweight, extensible, open source and cross-platform version of the popular Entity Framework data access technology

WHY USE ENTITY FRAMEWORK CORE?

EF Core can served as an object-relational mapper (O/RM)

 

  • Enables .NET developers to work with database using .NET objects.

 

  • Eliminates the need for most of the data-access code that typically needs to be written.

ENTITY FRAMEWOK LATEST VERSION

EF 6 EF CORE
Open-source Open-source
First released - 2008
with .NET Framework 3.5 SP1		 First realeased - June 2016
with .NET Core 1.0
Stable and feature rich New and evolving
Windows only Windows, Linux, OSX
Works on .NET Framework 3.5+ Works on .NET Framework 4.5+ and .NET Core

THE DIFFERENCES BETWEEN EF6 AND EF CORE

ENTITY FRAMEWOK CORE HISTORY

VERSION .NET FRAMEWORK
  EF Core 2.0   .NET Core 2.0
EF Core 1.1 .NET Core 1.1
 EF Core 1.0  .NET Core 1.0

Supported Application types, .NET Framework and OSs

EF Core Development Approaches

Supports 2 development approaches

  1. Code-First
  2. Database-First

EF Core Development Approaches

1 ) Code-First Approach

  • EF Core API creates the database and tables using migration based on the conventions and configuration provided in domain classes.
  • Useful in Domain Driven Design (DDD)

EF Core Development Approaches

2 ) Database-First Approach

  • EF Core API creates the domain and context classes based on existing database using EF Core commands.

 

  • This has limited support in EF Core as it does not support Visual Designer/Wizard

EF Core Database Provider

EF Core  uses a provider model to access many different database. 

EF Core includes providers as NuGet packages

- need to install

The Lists of Database providers & NuGet packages  

DATABASE NuGet PACKAGE
SQL SERVER Microsoft.EntityFrameworkCore.SqlServer
MySQL MySql.Data.EntityFrameworkCore
PostgreSQL Npgsql.EntityFrameworkCore.PostgreSQL
SQLite Microsoft.EntityFrameworkCore.SQLite
SQL Compact EntityFrameworkCore.SqlServerCompact40
In-memory Microsoft.EntityFrameworkCore.InMemory

DbContext

An integral part of Entity Framework

An instance of DbContext represents a session with the database which can be used to query and save instances of your entities to a database

Combination of the Unit OF Work and Repository patterns

DbContext functions

  1. Manage database connection

  2. Configure model & relationship

  3. Querying database

  4. Saving data to the database

  5. Configure change tracking

  6. Caching

  7. Transaction management

DbContext example

public class SchoolContext : DbContext
{
    public SchoolContext()
    {
  
    }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
    }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
    }
    //entities
    public DbSet<Student> Students { get; set; }
    public DbSet<Course> Courses { get; set; }
}

Ways to create / configuring a MODEL

  1. Use fluent API 

  2. Grouping

  3. Use data annotations

Use fluent API

using Microsoft.EntityFrameworkCore;

namespace EFModeling.FluentAPI.Required
{
    internal class MyContext : DbContext
    {
        public DbSet<Blog> Blogs { get; set; }

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

    public class Blog
    {
        public int BlogId { get; set; }
        public string Url { get; set; }
    }
}
  • Override the OnModelCreating method in derived context and use the ModelBuilder API to configure your model

Grouping

public class BlogEntityTypeConfiguration : IEntityTypeConfiguration<Blog>
{
    public void Configure(EntityTypeBuilder<Blog> builder)
    {
        builder
            .Property(b => b.Url)
            .IsRequired();
    }
}
  • To reduce the size of the OnModelCreating method all configuration for an entity type can be extracted to a separate class implementing IEntityTypeConfiguration<TEntity>

Use data annotations

using System.ComponentModel.DataAnnotations;
using Microsoft.EntityFrameworkCore;

namespace EFModeling.DataAnnotations.Required
{
    internal class MyContext : DbContext
    {
        public DbSet<Blog> Blogs { get; set; }
    }

    #region Required
    public class Blog
    {
        public int BlogId { get; set; }

        [Required]
        public string Url { get; set; }
    }
    #endregion
}
  • Data annotations will override conventions, but will be overridden by Fluent API configuration.
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