[ASP.NET MVC]Bài 5: Truy cập Cơ sở dữ liệu và sử dụng Linq

public class Product
{
    public int Id { get; set; }
    public string Name { get; set; }
    public string Description { get; set; }
    public decimal Price { get; set; }
}

public class ApplicationDbContext : DbContext
{
    public DbSet<Product> Products { get; set; }
}

<connectionStrings>
  <add name="ApplicationDbContext" connectionString="Server=(localdb)\MSSQLLocalDB;Database=MyDatabase;Trusted_Connection=True;MultipleActiveResultSets=true" providerName="System.Data.SqlClient" />
</connectionStrings>

public class ProductController : Controller
{
    private readonly ApplicationDbContext _context;

    public ProductController(ApplicationDbContext context)
    {
        _context = context;
    }

    public IActionResult Index()
    {
        var products = _context.Products.ToList();
        return View(products);
    }

    public IActionResult Create()
    {
        return View();
    }

    [HttpPost]
    public IActionResult Create(Product product)
    {
        _context.Products.Add(product);
        _context.SaveChanges();
        return RedirectToAction(nameof(Index));
    }

    public IActionResult Edit(int id)
    {
        var product = _context.Products.Find(id);
        return View(product);
    }

    [HttpPost]
    public IActionResult Edit(Product product)
    {
        _context.Products.Update(product);
        _context.SaveChanges();
        return RedirectToAction(nameof(Index));
    }

    public IActionResult Delete(int id)
    {
        var product = _context.Products.Find(id);
        return View(product);
    }

    [HttpPost, ActionName("Delete")]
    public IActionResult DeleteConfirmed(int id)
    {
        var product = _context.Products.Find(id);
        _context.Products.Remove(product);
        _context.SaveChanges();
        return RedirectToAction(nameof(Index));
    }
}

public class Sach
{
    public int Id { get; set; }
    public string TenSach { get; set; }
    public string TacGia { get; set; }
    public int NamXuatBan { get; set; }
}

public class SachDbContext : DbContext
{
    public DbSet<Sach> DanhSachSach { get; set; }
}

<connectionStrings>
    <add name="SachDbContext" connectionString="Data Source=(localdb)\MSSQLLocalDB;Initial Catalog=QuanLySach;Integrated Security=True;MultipleActiveResultSets=True;Application Name=EntityFramework" providerName="System.Data.SqlClient" />
</connectionStrings>

public class SachController : Controller
{
    private SachDbContext db = new SachDbContext();

    public ActionResult Index()
    {
        var danhSachSach = db.DanhSachSach.ToList();
        return View(danhSachSach);
    }

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

    [HttpPost]
    [ValidateAntiForgeryToken]
    public ActionResult Create(Sach sach)
    {
        if (ModelState.IsValid)
        {
            db.DanhSachSach.Add(sach);
            db.SaveChanges();
            return RedirectToAction("Index");
        }

        return View(sach);
    }

    // Các action khác tương tự
}

public class MyContext : DbContext
{
    public DbSet<Product> Products { get; set; }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        base.OnModelCreating(modelBuilder);

        // configures one-to-many relationship
        modelBuilder.Entity<Category>()
            .HasMany(g => g.Products)
            .WithRequired(s => s.Category)
            .HasForeignKey(s => s.CategoryId);
    }

    public class MyInitializer : DropCreateDatabaseAlways<MyContext>
    {
        protected override void Seed(MyContext context)
        {
            // add categories
            var categories = new List<Category>
            {
                new Category { Name = "Category 1" },
                new Category { Name = "Category 2" },
                new Category { Name = "Category 3" }
            };

            categories.ForEach(c => context.Categories.Add(c));
            context.SaveChanges();

            // add products
            var products = new List<Product>
            {
                new Product { Name = "Product 1", CategoryId = 1 },
                new Product { Name = "Product 2", CategoryId = 1 },
                new Product { Name = "Product 3", CategoryId = 2 },
                new Product { Name = "Product 4", CategoryId = 3 }
            };

            products.ForEach(p => context.Products.Add(p));
            context.SaveChanges();
        }
    }
}

Database.SetInitializer(new MyContext.MyInitializer());
var context = new MyContext();
context.Database.Initialize(true);

List<int> numbers = new List<int>() { 1, 2, 3, 4, 5 };

var filteredNumbers = from n in numbers
                      where n > 3
                      select n;

var filteredNumbers = numbers.Where(n => n > 3);

var filteredNames = from p in people
                    where p.Age > 18
                    select p.Name;

var filteredNames = people.Where(p => p.Age > 18).Select(p => p.Name);

var sortedNumbers = from n in numbers
                    orderby n descending
                    select n;

var sortedNumbers = numbers.OrderByDescending(n => n);

var groups = from p in people
             group p by p.Age into g
             select new { Age = g.Key, People = g };

var groups = people.GroupBy(p => p.Age)
                   .Select(g => new { Age = g.Key, People = g });

var result = from c in customers
             select new { Name = c.Name, Address = c.Address };

var result = customers.Select(c => new { Name = c.Name, Address = c.Address });

var result = from c in customers
             where c.City == "Hanoi"
             select c;

var result = customers.Where(c => c.City == "Hanoi");

var result = from c in customers
             orderby c.Name ascending
             select c;

var result = customers.OrderBy(c => c.Name);

var result = from c in customers
             group c by c.City into g
             select new { City = g.Key, Customers = g };

var result = customers.GroupBy(c => c.City)
                      .Select(g => new { City = g.Key, Customers = g });