autofac初識

在開始autofac時，有必要先瞭解兩個關鍵詞：“控制反轉(IoC/Inverse Of Control)”與“依賴註入(DI/Dependence injection)”。

控制反轉(IoC):它把傳統上由程式代碼直接操控的對象的調用權交給容器，通過容器來實現對象組件的裝配和管理。

依賴註入(DI):就是由IoC容器在運行期間，動態地將某種依賴關係註入到對象之中。

public class BMW 
    {
        /// <summary>
        /// 
        /// </summary>
        /// <param name="series">車系</param>
        public void Create(string series)
        {
            Console.WriteLine("生產了寶馬" + series);
        }
    }

    public class Porsche
    {
        /// <summary>
        /// 
        /// </summary>
        /// <param name="series">車系</param>
        public void Create(string series)
        {
            Console.WriteLine("生產了寶時捷" + series);
        }
    }

上面定義了寶馬與保時捷兩個類，它們都有Create方法，參數車系，傳統的調用方式如下：

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

這裡我們看到，需要使用new創建實例並調用方法

改進，使用工廠方式

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

    public class BMW : ICarCreator
    {
        /// <summary>
        /// 
        /// </summary>
        /// <param name="series">車系</param>
        public void Create(string series)
        {
            Console.WriteLine("生產了寶馬" + series);
        }
    }

    public class Porsche : ICarCreator
    {
        /// <summary>
        /// 
        /// </summary>
        /// <param name="series">車系</param>
        public void Create(string series)
        {
            Console.WriteLine("生產了寶時捷" + series);
        }
    }

調用方式，這裡使用了反射的形式，在配置文件里配置(類似支持多個資料庫的操作工廠)

            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>

進一步改進，使用autofac，將創建實例交給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("轎車");
}

完整的代碼如下：

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 普通的調用
            //BMW bmw = new BMW();
            //bmw.Create("730Li");
            //Porsche porsche = new Porsche();
            //porsche.Create("卡宴");
            #endregion

            #region 工廠的方式 
            //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("轎車");
            }
            #endregion

            Console.ReadKey();
        }
    }

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

    public class BMW : ICarCreator
    {
        /// <summary>
        /// 
        /// </summary>
        /// <param name="series">車系</param>
        public void Create(string series)
        {
            Console.WriteLine("生產了寶馬" + series);
        }
    }

    public class Porsche : ICarCreator
    {
        /// <summary>
        /// 
        /// </summary>
        /// <param name="series">車系</param>
        public void Create(string series)
        {
            Console.WriteLine("生產了寶時捷" + series);
        }
    }
}