CRUD using the Repository Pattern in MVC

using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;

namespace BookStore.Models
{
    public class Book
    {
        [Key]
        public int Id { get; set; }

        [Required]
        [MaxLength(30)]
        public string Title { get; set; }

        public string Authors { get; set; }

        [Column("Year")]
        [Display(Name = "Publish Year")]
        public string PublishYear { get; set; }

        [Column("Price")]
        [Display(Name = "Price")]
        public decimal BasePrice { get; set; }
    }
}

using System.Data.Entity;
using BookStore.Models;

namespace BookStore.DAL
{
    public class BookContext : DbContext
    {
        public BookContext()
            : base("name=BookStoreConnectionString")
        {
        }

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

<connectionStrings>
  <add name="BookStoreConnectionString" 
       connectionString="Data Source=sandeepss-PC;Initial Catalog=BookStore;User ID=shekhawat;Password=******" 
       providerName="System.Data.SqlClient" />
</connectionStrings>

Step 5. Create Repository.

In the DAL folder create an IBookRepository interface that has the filename IBookRepository.cs. This interface code declares a typical set of CRUD methods, including two read methods; one that returns all Book entity sets, and one that finds a single Book entity by ID.

using System;
using System.Collections.Generic;
using BookStore.Models;

namespace BookStore.DAL
{
    public interface IBookRepository : IDisposable
    {
        IEnumerable<Book> GetBooks();
        Book GetBookByID(int bookId);
        void InsertBook(Book book);
        void DeleteBook(int bookID);
        void UpdateBook(Book book);
        void Save();
    }
}

In the DAL folder, create a class file named "BookRepository.cs" The class file implements the "IBookRepository" interface and the "IBookRepository" inherits the IDisposable interface so the IDisposable interface is indirectly implemented by the BookRespository class. The database context is defined in a class variable, and the constructor expects the calling object to pass in an instance of the context.

Here we are passing the BookContext instance to the constructor.

using System;
using System.Collections.Generic;
using System.Linq;
using BookStore.Models;
using System.Data;

namespace BookStore.DAL
{
    public class BookRepository : IBookRepository
    {
        private BookContext _context;

        public BookRepository(BookContext bookContext)
        {
            this._context = bookContext;
        }

        public IEnumerable<Book> GetBooks()
        {
            return _context.Books.ToList();
        }

        public Book GetBookByID(int id)
        {
            return _context.Books.Find(id);
        }

        public void InsertBook(Book book)
        {
            _context.Books.Add(book);
        }

        public void DeleteBook(int bookID)
        {
            Book book = _context.Books.Find(bookID);
            _context.Books.Remove(book);
        }

        public void UpdateBook(Book book)
        {
            _context.Entry(book).State = EntityState.Modified;
        }

        public void Save()
        {
            _context.SaveChanges();
        }

        private bool disposed = false;

        protected virtual void Dispose(bool disposing)
        {
            if (!this.disposed)
            {
                if (disposing)
                {
                    _context.Dispose();
                }
            }
            this.disposed = true;
        }

        public void Dispose()
        {
            Dispose(true);
            GC.SuppressFinalize(this);
        }
    }
}

Step 6. Create Controller and Views for CRUD operations.

Now our model, data context, and repository are ready, so now proceed to the Controller. So we create a controller (BookController) for Book under the Controllers folder.

We need the following "using" in the controller to perform CRUD operations.

using System.Data;
using System.Linq;
using System.Web.Mvc;
using BookStore.DAL;
using BookStore.Models;

We create an instance of the Book repository interface in the Book Controller and initialize the book repository in the constructor of Book Controller (BookController.cs) as in the following.

private IBookRepository _bookRepository;

public BookController()
{
    this._bookRepository = new BookRepository(new BookContext());
}

We will use Scaffold templates to create a view for the CRUD operations. We use five scaffold templates, List, Create, Edit, Delete, and Details. So create a controller that has a post and get action results depending on the operation.

Operation 1. Show List of All Books.

Create an action in the controller named Index. The Index action returns a list of books.

public ActionResult Index()
{
    var books = from book in _bookRepository.GetBooks()
                select book;
    
    return View(books);
}

Now we create a view. To create the view use the following procedure.

1. Compile the source code successfully
2. Right-click on Action Method Index.
3. The View Name is already filled in so don't change it.
4. The View Engine already selected Razor so don't change it.
5. Check the checkbox "Create a strongly-typed view" because we are creating a strongly typed view.
6. Choose the Model class "Book" so it can be bound with the view.
7. Choose "List" from the Scaffold template so rapid development can be done and we get the view with the code for showing the list of Books.
8. Check both checkboxes "Reference script libraries" and "Use a layout or master page".

These are the common steps to follow for each operation and the only change will be the Scaffold template. The following picture shows the Index view that has a List Scaffold template.

Operation 2. Show Details of Book.

Create an action in the controller named Details. The Details action returns the details of the book.

public ViewResult Details(int id)
{
    Book book = _bookRepository.GetBookByID(id);
    return View(book);
}

Now we create the view. To create the view use the following procedure.

1. Right-click on Action Method Details.
2. The View Name is already filled in so don't change it.
3. The View Engine already selected Razor so don't change it.
4. Check the checkbox "Create a strongly-typed view" because we are creating a strongly typed-view.
5. Choose the Model class "Book" so it can be bound with the view.
6. Choose "Details" from the Scaffold template so we can do rapid development and get the view with the code for showing the details of the book.
7. Check both the checkboxes "Reference script libraries" and "Use a layout or master page".

Operation 3. Create a New Book.

Create two actions in the controller, one for the new book to create a view (Get Action) and another for submitting new book details to the repository (Post Action). These have the same name, Create.

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

[HttpPost]
public ActionResult Create(Book book)
{
    try
    {
        if (ModelState.IsValid)
        {
            _bookRepository.InsertBook(book);
            _bookRepository.Save();
            return RedirectToAction("Index");
        }
    }
    catch (DataException)
    {
        ModelState.AddModelError("", "Unable to save changes. Try again, and if the problem persists see your system administrator.");
    }
    
    return View(book);
}

Now we create a view. To create the view use the following procedure.

1. Right-click on the Action Method Create (GET).
2. The View Name is already filled in so don't change it.
3. The View Engine already selected Razor so don't change it.
4. Check the checkbox "Create a strongly-typed view" because we are creating a strongly typed-view.
5. Choose the Model class "Book" so it can be bound with the view.
6. Choose "Create" from the Scaffold template so we can do rapid development and we get the view for creating the new book.
7. Check both checkboxes "Reference script libraries" and "Use a layout or master page".

Operation 4. Update Book Details.

Create two actions in the controller, one for an existing book edit view (Get Action) and another for submitting the updated book details to the repository (Post Action). These have the same name Create. The Get action fills in the book details on the form by the id of the book so we would pass the id to the action.

public ActionResult Edit(int id)
{
    Book book = _bookRepository.GetBookByID(id);
    return View(book);
}

[HttpPost]
public ActionResult Edit(Book book)
{
    try
    {
        if (ModelState.IsValid)
        {
            _bookRepository.UpdateBook(book);
            _bookRepository.Save();
            return RedirectToAction("Index");
        }
    }
    catch (DataException)
    {
        ModelState.AddModelError("", "Unable to save changes. Try again, and if the problem persists see your system administrator.");
    }
    return View(book);
}

Now we create the view. To create the view use the following procedure.

1. Right-click on Action Method Edit (GET).
2. The View Name is already filled in so don't change it.
3. The View Engine already selected Razor so don't change it.
4. Check the checkbox "Create a strongly-typed view" because we are creating a strongly typed-view.
5. Choose the Model class "Book" so it can be bound with the view.
6. Choose "Edit" from the Scaffold template so we can do rapid development and get the view for updating an existing book.
7. Check both checkboxes "Reference script libraries" and "Use a layout or master page".

Operation 5. Delete Book.

Create two actions in the controller, one to show the details of the book after clicking on the Delete link (Get Action) and another to Delete the book (Post Action). One Delete action but another overrides the Delete Action that overrides the DeleteConfirmed method. The Get action fills in book details on the form by the ID of the book, and then the Post action is performed on it.

public ActionResult Delete(int id, bool? saveChangesError)
{
    if (saveChangesError.GetValueOrDefault())
    {
        ViewBag.ErrorMessage = "Unable to save changes. Try again, and if the problem persists see your system administrator.";
    }
    
    Book book = _bookRepository.GetBookByID(id);
    return View(book);
}

[HttpPost, ActionName("Delete")]
public ActionResult DeleteConfirmed(int id)
{
    try
    {
        Book book = _bookRepository.GetBookByID(id);
        _bookRepository.DeleteBook(id);
        _bookRepository.Save();
    }
    catch (DataException)
    {
        return RedirectToAction("Delete", new System.Web.Routing.RouteValueDictionary
        {
            { "id", id },
            { "saveChangesError", true }
        });
    }
    
    return RedirectToAction("Index");
}

Now we create the view. To create the view use the following procedure.

1. Right-click on Action Method Delete.
2. The View Name is already filled in so don't change it.
3. The View Engine already selected Razor so don't change it.
4. Check the checkbox "Create a strongly-typed view" because we are creating a strongly typed-view.
5. Choose the Model class "Book" so it can be bound with the view.
6. Choose "Delete" from the Scaffold template so we can do rapid development and get the view of the delete for the existing book.
7. Check both checkboxes "Reference script libraries" and "Use a layout or master page".

Now the view and action are ready to perform CRUD operations.

Step 7. Run the application.

Call the Book controller http://localhost:4736/Book from the browser and we get the default empty list of books.

Check that our database is created by the data context when the application calls the book entity.

Create new books.

Click on the "Create" button and a new book is created.

Now click on the "Edit" link button of a row and show the book details in the edited form.

Click on the "Save" button and see the updated book list.

Now click on the "Details" button and we get the details of the book.

Click on the back to list and now click on the delete link button then we get the delete confirmation window.

Click on the delete button and the book is deleted.

We perform all CRUD operations successfully. I didn't use many basic screenshots here to create the controller, model, and views because I know that you are already familiar with these. If you want to know more about the basics of MVC razors then here is my other article.

Getting Started with Razor View Engine in MVC 3

I attached source code (Models, Views, Controllers folder, and web. config file) for this book store application so you can try to develop it. Feel free to post a comment on any issue and questions that you find during the development of this application.