Repository Pattern

The Repository Pattern is one of the most popular patterns to create an enterprise level application. It restricts us to work directly with the data in the application and creates new layers for database operations, business logic and the application’s UI. 

Using the Repository Pattern has many advantages:

• Your business logic can be unit tested without data access logic;
• The database access code can be reused;
• Your database access code is centrally managed so easy to implement any database access policies, like caching;
• It’s easy to implement domain logics;
• Your domain entities or business entities are strongly typed with annotations; and more.

Repository Class

This is the class which will perform database operations on the Product Entity. In this class, we will implement the IProductRepository interface from the Core project. Let us start with adding a class ProductRepository to the Infrastructure project and implement IProductRepository interface. To perform database operations, we are going to write simple LINQ to Entity queries. ProductRepositry class can be created as shown in the listing below:

using ProductApp.Core.Interfaces;
using System.Collections.Generic;
using System.Linq;
using ProductApp.Core;

namespace ProductApp.Infrastructure
{
    public class ProductRepository : IProductRepository
    {
        ProductContext context = new ProductContext();
        public void Add(Product p)
        {
            context.Products.Add(p);
            context.SaveChanges();
        }

        public void Edit(Product p)
        {
            context.Entry(p).State = System.Data.Entity.EntityState.Modified;
        }

        public Product FindById(int Id)
        {
            var result = (from r in context.Products where r.Id == Id select r).FirstOrDefault();
            return result;
        }

        public IEnumerable GetProducts() { return context.Products; } public void Remove(int Id) { Product p = context.Products.Find(Id); context.Products.Remove(p); context.SaveChanges(); } } } 

So far we have created a Data Context class, a Database Initializer class, and the Repository class. Let us build the infrastructure project to make sure that everything is in place.