Entity Framework 自动生成CodeFirst代码

前言

在前面的文章中我们提到Entity Framework的“Code First”模式也同样可以基于现有数据库进行开发。今天就让我们一起看一下使用Entity Framework Power Tools如何基于现有数据库生成数据类和数据库上下等。

Entity Framework Power Tools

基于现有数据库生成POCO数据类和数据库上下文需要借助Visual Studio一个扩展插件-- Entity Framework Power Tools（一个Code First反向工程工具）。

通过点击上图的扩展和更新，得到如下图所示的界面

安装完之后只要在项目上右键选择Entity Framework->Reverse Engineer Code First（项目中首先需要安装Entity Framework 包，否则会有错误），然后在弹出的窗口中输入相关的数据库连接信息即可（我们这里使用“NorthWind”数据库）。

当然当你在操作的时候你首先还是要先引用Entity Framework。然后点击Reverse Engineer Code First

配置好数据库链接，

确认之后，我们首先来看一下配置文件的变化

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <configSections>
    <!-- For more information on Entity Framework configuration, visit http://go.microsoft.com/fwlink/?LinkID=237468 -->
    <section name="entityFramework" type="System.Data.Entity.Internal.ConfigFile.EntityFrameworkSection, EntityFramework, Version=5.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" requirePermission="false" />
  </configSections>
  <connectionStrings>
    <add name="NorthwindContext" connectionString="Data Source=.;Initial Catalog=Northwind;Integrated Security=True;MultipleActiveResultSets=True"
      providerName="System.Data.SqlClient" />
  </connectionStrings>
  <startup>
    <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5" />
  </startup>
  <entityFramework>
    <defaultConnectionFactory type="System.Data.Entity.Infrastructure.LocalDbConnectionFactory, EntityFramework">
      <parameters>
        <parameter value="v11.0" />
      </parameters>
    </defaultConnectionFactory>
  </entityFramework>
</configuration>

于此同时生成了NorthWindContext数据库操作上下文

using System.Data.Entity;
using System.Data.Entity.Infrastructure;
using CodeFirstPowerTools.Models.Mapping;

namespace CodeFirstPowerTools.Models
{
    public partial class NorthwindContext : DbContext
    {
        static NorthwindContext()
        {
            Database.SetInitializer<NorthwindContext>(null);
        }

        public NorthwindContext()
            : base("Name=NorthwindContext")
        {
        }

        public DbSet<Category> Categories { get; set; }
        public DbSet<CustomerDemographic> CustomerDemographics { get; set; }
        public DbSet<Customer> Customers { get; set; }
        public DbSet<Employee> Employees { get; set; }
        public DbSet<Order_Detail> Order_Details { get; set; }
        public DbSet<Order> Orders { get; set; }
        public DbSet<Product> Products { get; set; }
        public DbSet<Region> Regions { get; set; }
        public DbSet<Shipper> Shippers { get; set; }
        public DbSet<Supplier> Suppliers { get; set; }
        public DbSet<Territory> Territories { get; set; }
        public DbSet<Alphabetical_list_of_product> Alphabetical_list_of_products { get; set; }
        public DbSet<Category_Sales_for_1997> Category_Sales_for_1997 { get; set; }
        public DbSet<Current_Product_List> Current_Product_Lists { get; set; }
        public DbSet<Customer_and_Suppliers_by_City> Customer_and_Suppliers_by_Cities { get; set; }
        public DbSet<Invoice> Invoices { get; set; }
        public DbSet<Order_Details_Extended> Order_Details_Extendeds { get; set; }
        public DbSet<Order_Subtotal> Order_Subtotals { get; set; }
        public DbSet<Orders_Qry> Orders_Qries { get; set; }
        public DbSet<Product_Sales_for_1997> Product_Sales_for_1997 { get; set; }
        public DbSet<Products_Above_Average_Price> Products_Above_Average_Prices { get; set; }
        public DbSet<Products_by_Category> Products_by_Categories { get; set; }
        public DbSet<Sales_by_Category> Sales_by_Categories { get; set; }
        public DbSet<Sales_Totals_by_Amount> Sales_Totals_by_Amounts { get; set; }
        public DbSet<Summary_of_Sales_by_Quarter> Summary_of_Sales_by_Quarters { get; set; }
        public DbSet<Summary_of_Sales_by_Year> Summary_of_Sales_by_Years { get; set; }

        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            modelBuilder.Configurations.Add(new CategoryMap());
            modelBuilder.Configurations.Add(new CustomerDemographicMap());
            modelBuilder.Configurations.Add(new CustomerMap());
            modelBuilder.Configurations.Add(new EmployeeMap());
            modelBuilder.Configurations.Add(new Order_DetailMap());
            modelBuilder.Configurations.Add(new OrderMap());
            modelBuilder.Configurations.Add(new ProductMap());
            modelBuilder.Configurations.Add(new RegionMap());
            modelBuilder.Configurations.Add(new ShipperMap());
            modelBuilder.Configurations.Add(new SupplierMap());
            modelBuilder.Configurations.Add(new TerritoryMap());
            modelBuilder.Configurations.Add(new Alphabetical_list_of_productMap());
            modelBuilder.Configurations.Add(new Category_Sales_for_1997Map());
            modelBuilder.Configurations.Add(new Current_Product_ListMap());
            modelBuilder.Configurations.Add(new Customer_and_Suppliers_by_CityMap());
            modelBuilder.Configurations.Add(new InvoiceMap());
            modelBuilder.Configurations.Add(new Order_Details_ExtendedMap());
            modelBuilder.Configurations.Add(new Order_SubtotalMap());
            modelBuilder.Configurations.Add(new Orders_QryMap());
            modelBuilder.Configurations.Add(new Product_Sales_for_1997Map());
            modelBuilder.Configurations.Add(new Products_Above_Average_PriceMap());
            modelBuilder.Configurations.Add(new Products_by_CategoryMap());
            modelBuilder.Configurations.Add(new Sales_by_CategoryMap());
            modelBuilder.Configurations.Add(new Sales_Totals_by_AmountMap());
            modelBuilder.Configurations.Add(new Summary_of_Sales_by_QuarterMap());
            modelBuilder.Configurations.Add(new Summary_of_Sales_by_YearMap());
        }
    }
}

最终来查看一下生成的文件

代码调用实例

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using CodeFirstPowerTools.Models;

namespace CodeFirstPowerTools
{
    class Program
    {
        static void Main(string[] args)
        {
            using (var db = new NorthwindContext())
            {
                IQueryable<Order> orders = from order in db.Orders
                                           where order.OrderID < 10256
                                           select order;
                foreach (Order order in orders)
                {
                    Console.WriteLine(order.ShipCity);
                }
            }
            Console.ReadLine();
        }
    }
}

执行后结果如下

简单的使用到此为止。