CRUD Operations Using Entity Framework 5.0 Code First Approach in MVC

public DbSet<Publisher> Publishers { get; set; }
public DbSet<Book> Books { get; set; }

The Dbset property represents an entity set used to perform create, read, update, and delete operations. A non-generic version of DbSet<TEntity> can be used when the type of entity is not known at build time. Here we are using the plural name of the property for an entity, which means your table will be created with this name in the database for that specific entity.

Method

The LibraryContext class has an override OnModelCreating method. This method is called when the model for a derived context has been initialized, but before the model has been locked down and used to initialize the context. The default implementation of this method does nothing, but it can be overridden in a derived class such that the model can be further configured before it is locked down. Basically in this method, we configure the database table that will be created by a model or a defined relationship among those tables.

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
    modelBuilder.Entity<Publisher>().HasKey(p => p.PublisherId);
    modelBuilder.Entity<Publisher>().Property(c => c.PublisherId)
        .HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);
    modelBuilder.Entity<Book>().HasKey(b => b.BookId);
    modelBuilder.Entity<Book>().Property(b => b.BookId)
        .HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);
    modelBuilder.Entity<Book>().HasRequired(p => p.Publisher)
        .WithMany(b => b.Books).HasForeignKey(b => b.PublisherId);
    base.OnModelCreating(modelBuilder);
}

This method accepts one parameter, an object of DbModelBuilder. This DbModelBuilder class maps POCO classes to the database schema. This method is called only once when the first instance of a derived context is created. The model for that context is then cached and is for all further instances of the context in the app domain. This caching can be disabled by setting the ModelCaching property on the given ModelBuidler, but this can seriously degrade performance. More control over caching is provided through use of the DbModelBuilder and DbContext classes directly.

Configure/Mapping properties with the Fluent API

The OnModelCreating() method under the LibraryContext class uses the Fluent API to map and configure properties in the table. So let's see each method used in the OnModelCreating() method one by one.

1. HasKey(): The Haskey() method configures a primary key on the table.
2. Property(): The Property method configures attributes for each property belonging to an entity or complex type. It is used to obtain a configuration object for a given property. The options on the configuration object are specific to the type being configured; IsUnicode is available only on string properties for example.
3. HasDatabaseGeneratedOption: It configures how values for the property are generated by the database.
4. DatabaseGeneratedOption.Identity: DatabaseGeneratedOption is database annotation. It enumerates a database-generated option. DatabaseGeneratedOption.Identity is used to create an auto-increment column in the table by unique value.
5. The foreign key relation is defined between the Publisher and the Book using the following expression.

   modelBuilder.Entity<Book>()
       .HasRequired(p => p.Publisher)
       .WithMany(b => b.Books)
       .HasForeignKey(b => b.PublisherId);
   

Create Controller for CRUD Operations

Now we create two controllers, one for Publisher CRUD operations (PublisherController.cs) and another for Book CRUD operations (BookController.cs) under the Controllers folder in the application. So here is the code for each.

The Publisher controller is in the file PublisherController.cs in the Controllers folder.

using System.Linq;
using System.Web.Mvc;
using ExampleCodeFirstApproch.Models;

namespace ExampleCodeFirstApproch.Controllers
{
    public class PublisherController : Controller
    {
        LibraryContext objContext;

        public PublisherController()
        {
            objContext = new LibraryContext();
        }

        #region List and Details Publisher
        public ActionResult Index()
        {
            var publishers = objContext.Publishers.ToList();
            return View(publishers);
        }

        public ViewResult Details(int id)
        {
            Publisher publisher = objContext.Publishers.Where(x => x.PublisherId == id).SingleOrDefault();
            return View(publisher);
        }
        #endregion

        #region Create Publisher
        public ActionResult Create()
        {
            return View(new Publisher());
        }

        [HttpPost]
        public ActionResult Create(Publisher publish)
        {
            objContext.Publishers.Add(publish);
            objContext.SaveChanges();
            return RedirectToAction("Index");
        }
        #endregion

        #region Edit publisher
        public ActionResult Edit(int id)
        {
            Publisher publisher = objContext.Publishers.Where(x => x.PublisherId == id).SingleOrDefault();
            return View(publisher);
        }

        [HttpPost]
        public ActionResult Edit(Publisher model)
        {
            Publisher publisher = objContext.Publishers.Where(x => x.PublisherId == model.PublisherId).SingleOrDefault();
            if (publisher != null)
            {
                objContext.Entry(publisher).CurrentValues.SetValues(model);
                objContext.SaveChanges();
                return RedirectToAction("Index");
            }
            return View(model);
        }
        #endregion

        #region Delete Publisher
        public ActionResult Delete(int id)
        {
            Publisher publisher = objContext.Publishers.Find(id);
            return View(publisher);
        }

        [HttpPost]
        public ActionResult Delete(int id, Publisher model)
        {
            var publisher = objContext.Publishers.Where(x => x.PublisherId == id).SingleOrDefault();
            if (publisher != null)
            {
                objContext.Publishers.Remove(publisher);
                objContext.SaveChanges();
            }
            return RedirectToAction("Index");
        }
        #endregion
    }
}

The Book controller is in the file BookController.cs in the Controllers folder.

using System.Linq;
using System.Web.Mvc;
using ExampleCodeFirstApproch.Models;

namespace ExampleCodeFirstApproch.Controllers
{
    public class BookController : Controller
    {
        LibraryContext objContext;

        public BookController()
        {
            objContext = new LibraryContext();
        }

        #region List and Details Book
        public ActionResult Index()
        {
            var books = objContext.Books.ToList();
            return View(books);
        }

        public ViewResult Details(int id)
        {
            Book book = objContext.Books.Where(x => x.BookId == id).SingleOrDefault();
            return View(book);
        }
        #endregion

        #region Create Publisher
        public ActionResult Create()
        {
            return View(new Book());
        }

        [HttpPost]
        public ActionResult Create(Book book)
        {
            objContext.Books.Add(book);
            objContext.SaveChanges();
            return RedirectToAction("Index");
        }
        #endregion

        #region Edit Book
        public ActionResult Edit(int id)
        {
            Book book = objContext.Books.Where(x => x.BookId == id).SingleOrDefault();
            return View(book);
        }

        [HttpPost]
        public ActionResult Edit(Book model)
        {
            Book book = objContext.Books.Where(x => x.BookId == model.BookId).SingleOrDefault();
            if (book != null)
            {
                objContext.Entry(book).CurrentValues.SetValues(model);
                objContext.SaveChanges();
                return RedirectToAction("Index");
            }
            return View(model);
        }
        #endregion

        #region Delete Book
        public ActionResult Delete(int id)
        {
            Book book = objContext.Books.Find(id);
            return View(book);
        }

        [HttpPost]
        public ActionResult Delete(int id, Publisher model)
        {
            var book = objContext.Books.Where(x => x.BookId == id).SingleOrDefault();
            if (book != null)
            {
                objContext.Books.Remove(book);
                objContext.SaveChanges();
            }
            return RedirectToAction("Index");
        }
        #endregion
    }
}

Both Publisher and Book controllers are ready and create a view according to the action method using a scaffold template and you can download a zip folder. Run the application and you get that your tables are created in the database with a relationship.

Figure 2. Relationship between Publishers and Books Tables

Note. Download the source code then change the connection string in the web. config file and run the application.