Getting Started - Entity Framework Code First


Entity Framework Code First

 - This article is Part of a series :


  • open visual studio and Create a new web application named Library
  • Select Empty template and click OK
  • From the Tools menu click NuGet Package Manager and then click Package Manager Console. In the Package Manager Console write the following command: 
PM> Install-Package EntityFramework

- Create the Data Model

  • add new folder named Models then Create 2 classes named Author.cs  and Book.cs and write the following Code : 
//Author.cs
using System;
using System.Collections.Generic;

namespace Library.Models
{
    public class Author
    {
        public int AuthorId { get; set; }
        public string AuthorName { get; set; }
        public virtual ICollection<Book> Books { get; set; }
    }

}

   
//Book.cs

namespace Library.Models
{
    public class Book
    {
        public int BookId { get; set; }
        public string BookName { get; set; }
        public int AuthorId { get; set; }
        public virtual Author Author { get; set; }
    }

}

- Create the Database Context

  • Create new folder named DataLayer and add new class named LibraryDbContext.cs and write the following Code : 
//LibraryDbContext.cs


using Library.Models;
using System;
using System.Collections.Generic;
using System.Data.Entity;

namespace Library.DataLayer
{
    public class LibraryDbContext : DbContext
    {
        public LibraryDbContext()
            : base("DefaultConnection")
        {

        }


        public DbSet<Book> Books { get; set; }
        public DbSet<Author> Authors { get; set; }


        public static LibraryDbContext Create()
        {
            return new LibraryDbContext();
        }
    }

}

  • From the Tools menu click NuGet Package Manager and then click Package Manager Console. In the Package Manager Console write the following command:
PM> Enable-Migrations
  • After enabling migrations has done add to seed method in Configuration class follwing :

//Configuration.cs
protected override void Seed(Library.DataLayer.LibraryDbContext context)
        {
            context.Authors.AddOrUpdate(a => a.AuthorName, new Author { AuthorName = "Stephen Hawking" });
            context.Authors.AddOrUpdate(a => a.AuthorName, new Author { AuthorName = "Elisabeth Kübler-Ross" });
            context.Authors.AddOrUpdate(a => a.AuthorName, new Author { AuthorName = "Tony Crilly" });
            context.SaveChanges();
            context.Books.AddOrUpdate(a => a.BookName, new Book { BookName = "A brief history of time" , AuthorId = context.Authors.Single(a => a.AuthorName == "Stephen Hawking").AuthorId });
            context.Books.AddOrUpdate(a => a.BookName, new Book { BookName = "Death: The Final Stage of Growth"  , AuthorId = context.Authors.Single(a => a.AuthorName == "Elisabeth Kübler-Ross").AuthorId });
            context.Books.AddOrUpdate(a => a.BookName, new Book { BookName = "50 Mathematical Ideas You Really Need to Know" , AuthorId = context.Authors.Single(a => a.AuthorName == "Tony Crilly").AuthorId });
            context.Books.AddOrUpdate(a => a.BookName, new Book { BookName = "The Grand Design" , AuthorId = context.Authors.Single(a => a.AuthorName == "Stephen Hawking").AuthorId });

        }


PM> Add-Migration initial-libraryDbContext
  • In the generated  migration class turn cascadeDelete to false 
//initiallibraryDbContext

    public partial class initiallibraryDbContext : DbMigration
    {
        public override void Up()
        {
            CreateTable(
                "dbo.Authors",
                c => new
                    {
                        AuthorId = c.Int(nullable: false, identity: true),
                        AuthorName = c.String(),
                    })
                .PrimaryKey(t => t.AuthorId);
           
            CreateTable(
                "dbo.Books",
                c => new
                    {
                        BookId = c.Int(nullable: false, identity: true),
                        BookName = c.String(),
                        AuthorId = c.Int(nullable: false),
                    })
                .PrimaryKey(t => t.BookId)
                .ForeignKey("dbo.Authors", t => t.AuthorId, cascadeDelete: false)
                .Index(t => t.AuthorId);
           
        }
       
        public override void Down()
        {
            DropForeignKey("dbo.Books", "AuthorId", "dbo.Authors");
            DropIndex("dbo.Books", new[] { "AuthorId" });
            DropTable("dbo.Books");
            DropTable("dbo.Authors");
        }
    }


  • Right click on your project, select Add, then Add ASP.Net Folder and choose the App_Data folder
PM> Update-Database -Verbose

  • That is all! now we have our database working and you can explorer it , Next article will be in how to create ASP.NET RESTful APIs (web api) .
- link to project in github.