autofac初识

在开始autofac时，有必要先了解两个关键词：“控制反转(IoC/Inverse Of Control)”与“依赖注入(DI/Dependence injection)”。

控制反转(IoC):它把传统上由程序代码直接操控的对象的调用权交给容器，通过容器来实现对象组件的装配和管理。

依赖注入(DI):就是由IoC容器在运行期间，动态地将某种依赖关系注入到对象之中。

public class BMW
    {
        /// <summary>
        ///
        /// </summary>
        /// <param name="series">车系</param>
        public void Create(string series)
        {
            Console.WriteLine("生产了宝马" + series);
        }
    }

    public class Porsche
    {
        /// <summary>
        ///
        /// </summary>
        /// <param name="series">车系</param>
        public void Create(string series)
        {
            Console.WriteLine("生产了宝时捷" + series);
        }
    }

上面定义了宝马与保时捷两个类，它们都有Create方法，参数车系，传统的调用方式如下：

BMW bmw = new BMW();
bmw.Create("730Li");
Porsche porsche = new Porsche();
porsche.Create("卡宴");

这里我们看到，需要使用new创建实例并调用方法

改进，使用工厂方式

public interface ICarCreator
    {
        void Create(string series);
    }

    public class BMW : ICarCreator
    {
        /// <summary>
        ///
        /// </summary>
        /// <param name="series">车系</param>
        public void Create(string series)
        {
            Console.WriteLine("生产了宝马" + series);
        }
    }

    public class Porsche : ICarCreator
    {
        /// <summary>
        ///
        /// </summary>
        /// <param name="series">车系</param>
        public void Create(string series)
        {
            Console.WriteLine("生产了宝时捷" + series);
        }
    }

调用方式，这里使用了反射的形式，在配置文件里配置(类似支持多个数据库的操作工厂)

            ICarCreator car = (ICarCreator)Assembly.GetExecutingAssembly().CreateInstance(ConfigurationManager.AppSettings["Brand"]);   //使用了反射方式
            car.Create("suv");

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <appSettings>
    <add key="Brand" value="AutofacDemo1.BMW"/>
  </appSettings>
    <startup>
        <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5" />
    </startup>
</configuration>

进一步改进，使用autofac，将创建实例交给autofac

var builder = new ContainerBuilder();

builder.RegisterType<ICarCreator>();
builder.RegisterType<BMW>().As<ICarCreator>();
//builder.RegisterType<Porsche>().As<ICarCreator>();
Container = builder.Build();
using (var scope = Container.BeginLifetimeScope())
{
    var writer = scope.Resolve<ICarCreator>();
    writer.Create("轿车");
}

完整的代码如下：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using System.Text;
using System.Threading.Tasks;
using System.Configuration;
using Autofac;

namespace AutofacDemo1
{
    class Program
    {
        private static IContainer Container { get; set; }
        static void Main(string[] args)
        {
            #region 普通的调用
            //BMW bmw = new BMW();
            //bmw.Create("730Li");
            //Porsche porsche = new Porsche();
            //porsche.Create("卡宴");
            #endregion

            #region 工厂的方式
            //ICarCreator car = (ICarCreator)Assembly.GetExecutingAssembly().CreateInstance(ConfigurationManager.AppSettings["Brand"]);   //使用了反射方式
            //car.Create("suv");
            #endregion

            #region 使用Ioc[Autofac]
            var builder = new ContainerBuilder();

            builder.RegisterType<ICarCreator>();
            builder.RegisterType<BMW>().As<ICarCreator>();
            //builder.RegisterType<Porsche>().As<ICarCreator>();
            Container = builder.Build();
            using (var scope = Container.BeginLifetimeScope())
            {
                var writer = scope.Resolve<ICarCreator>();
                writer.Create("轿车");
            }
            #endregion

            Console.ReadKey();
        }
    }

    public interface ICarCreator
    {
        void Create(string series);
    }

    public class BMW : ICarCreator
    {
        /// <summary>
        ///
        /// </summary>
        /// <param name="series">车系</param>
        public void Create(string series)
        {
            Console.WriteLine("生产了宝马" + series);
        }
    }

    public class Porsche : ICarCreator
    {
        /// <summary>
        ///
        /// </summary>
        /// <param name="series">车系</param>
        public void Create(string series)
        {
            Console.WriteLine("生产了宝时捷" + series);
        }
    }
}