Entity Framework(EF框架)

• Entity Framework負(fù)責(zé)將模型與數(shù)據(jù)庫關(guān)聯(lián)起來
• Entity Framework需要兩件事以實(shí)現(xiàn)它的上述目的

1. 創(chuàng)建一個(gè)上下文類(MyStoreEntities)==>連接到數(shù)據(jù)庫后Entity Framework會(huì)自動(dòng)生成它
2. 在連接到數(shù)據(jù)庫后，在web.config文件中增添連接串，這個(gè)連接串的名字與上下文類的名字相同==>需要開發(fā)者手動(dòng)添加

<connectionStrings>
    <add name="MyStoreEntities" connectionString="metadata=res://*/Concrete.MyStore.csdl|res://*/Concrete.MyStore.ssdl|res://*/Concrete.MyStore.msl;provider=System.Data.SqlClient;provider connection string=&quot;data source=DESKTOP-6SVSFQS\SQLEXPRESS;initial catalog=MyStore;integrated security=True;MultipleActiveResultSets=True;App=EntityFramework&quot;" providerName="System.Data.EntityClient" />
  </connectionStrings>

MyStoreEntities

public partial class MyStoreEntities : DbContext
    {
        public MyStoreEntities()
            : base("name=MyStoreEntities")
        {
        }
        ......
        public virtual DbSet<Category> Category { get; set; }
        public virtual DbSet<Order> Product { get; set; }
        ......
    }

• MyStoreEntities繼承于上下文類DbContext
• MyStoreEntities具有DbSet(模型)類型的屬性，其值對(duì)應(yīng)數(shù)據(jù)庫的每張表
• 我們通常通過MyStoreEntities的實(shí)例來對(duì)數(shù)據(jù)庫進(jìn)行讀寫，具體有如下應(yīng)用

實(shí)現(xiàn)存儲(chǔ)庫類

public class EFProductRepository:IProductsRepository
    {
        private MyStoreEntities db = new MyStoreEntities();
        public IQueryable<Product> Products
        {
            get { return db.Product; }
        }
        public IQueryable<Category> Categories
        {
            get { return db.Category; }
        }
        public IQueryable<Customer> Customers
        {
            get { return db.Customer; }
        }
    }

實(shí)現(xiàn)業(yè)務(wù)處理類

  public class DatabaseOrderProcessor : IOrderProcessor
    {
        public void ProcessOrder(Cart cart, ShippingAddress shippingInfo, Customer customer)
        {         
                       var db = new MyStoreEntities()
                        Order order = new Order();
                        order.CustomerId = customer.Id;
                        order.OrderDate = DateTime.Now;
                        .......
                        db.Order.Add(order);//修改db屬性
                        db.SaveChanges();//db向數(shù)據(jù)庫提交改變
            }
        }
    }