// The Repository Pattern is a design pattern commonly used in C# applications to separate the data access logic from the business logic.

// This pattern aims to create a layer that isolates the database access, enabling a more modular, maintainable, and testable codebase.

// Here's a basic example to demonstrate how to implement the Repository Pattern in C#.

public class Product

{

public int Id { get; set; }

public string Name { get; set; }

public decimal Price { get; set; }

}

using System.Collections.Generic;

public interface IProductRepository

{

IEnumerable<Product> GetAll();

Product GetById(int id);

void Add(Product product);

void Update(Product product);

void Delete(int id);

}

using System.Collections.Generic;

using System.Linq;

using Microsoft.EntityFrameworkCore;

public class ProductRepository : IProductRepository

{

private readonly AppDbContext _context;

public ProductRepository(AppDbContext context)

{

_context = context;

}

public IEnumerable<Product> GetAll()

{

return _context.Products.ToList();

}

public Product GetById(int id)

{

return _context.Products.Find(id);

}

public void Add(Product product)

{

_context.Products.Add(product);

_context.SaveChanges();

}

public void Update(Product product)

{

_context.Products.Update(product);

_context.SaveChanges();

}

public void Delete(int id)

{

var product = _context.Products.Find(id);

if (product != null)

{

_context.Products.Remove(product);

_context.SaveChanges();

}

}

}

using Microsoft.EntityFrameworkCore;

public class AppDbContext : DbContext

{

public DbSet<Product> Products { get; set; }

public AppDbContext(DbContextOptions<AppDbContext> options) : base(options)

{

}

}

public void ConfigureServices(IServiceCollection services)

{

services.AddDbContext<AppDbContext>(options =>

options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection")));

services.AddScoped<IProductRepository, ProductRepository>();

services.AddControllersWithViews();

}

using Microsoft.AspNetCore.Mvc;

using System.Collections.Generic;

public class ProductsController : Controller

{

private readonly IProductRepository _productRepository;

public ProductsController(IProductRepository productRepository)

{

_productRepository = productRepository;

}

public IActionResult Index()

{

IEnumerable<Product> products = _productRepository.GetAll();

return View(products);

}

public IActionResult Details(int id)

{

Product product = _productRepository.GetById(id);

if (product == null)

{

return NotFound();

}

return View(product);

}

// Add other actions for Create, Update, and Delete operations

}

///// setup unit tests /////

dotnet add package Microsoft.EntityFrameworkCore.InMemory

dotnet add package Moq

dotnet add package xunit

dotnet add package xunit.runner.visualstudio

dotnet add package Microsoft.NET.Test.Sdk

using System.Collections.Generic;

using System.Linq;

using Microsoft.EntityFrameworkCore;

using Moq;

using Xunit;

public class ProductRepositoryTests

{

private DbContextOptions<AppDbContext> _dbContextOptions;

public ProductRepositoryTests()

{

_dbContextOptions = new DbContextOptionsBuilder<AppDbContext>()

.UseInMemoryDatabase(databaseName: "TestDatabase")

.Options;

using (var context = new AppDbContext(_dbContextOptions))

{

context.Products.Add(new Product { Id = 1, Name = "Product1", Price = 10 });

context.Products.Add(new Product { Id = 2, Name = "Product2", Price = 20 });

context.SaveChanges();

}

}

[Fact]

public void GetAll_ReturnsAllProducts()

{

using (var context = new AppDbContext(_dbContextOptions))

{

var repository = new ProductRepository(context);

var products = repository.GetAll().ToList();

Assert.Equal(2, products.Count);

Assert.Equal("Product1", products[0].Name);

Assert.Equal("Product2", products[1].Name);

}

}

[Fact]

public void GetById_ReturnsCorrectProduct()

{

using (var context = new AppDbContext(_dbContextOptions))

{

var repository = new ProductRepository(context);

var product = repository.GetById(1);

Assert.NotNull(product);

Assert.Equal("Product1", product.Name);

}

}

[Fact]

public void Add_AddsProductToDatabase()

{

using (var context = new AppDbContext(_dbContextOptions))

{

var repository = new ProductRepository(context);

var newProduct = new Product { Id = 3, Name = "Product3", Price = 30 };

repository.Add(newProduct);

var product = repository.GetById(3);

Assert.NotNull(product);

Assert.Equal("Product3", product.Name);

}

}

[Fact]

public void Update_UpdatesExistingProduct()

{

using (var context = new AppDbContext(_dbContextOptions))

{

var repository = new ProductRepository(context);

var product = repository.GetById(1);

product.Name = "UpdatedProduct";

repository.Update(product);

var updatedProduct = repository.GetById(1);

Assert.Equal("UpdatedProduct", updatedProduct.Name);

}

}

[Fact]

public void Delete_RemovesProductFromDatabase()

{

using (var context = new AppDbContext(_dbContextOptions))

{

var repository = new ProductRepository(context);

repository.Delete(1);

var product = repository.GetById(1);

Assert.Null(product);

}

}

}