一、配置Autofac替换内置DI

1.安装Nuget包：Autofac.Extensions.DependencyInjection

2.Program.cs中加上

(资料图片仅供参考)

builder.Host.UseServiceProviderFactory(new AutofacServiceProviderFactory());builder.Host.ConfigureContainer(containerBuilder =>{    //在这里写注入代码    });

二、构造函数注入

新建IUserService，类UserService

public interface IUserService    {        public string GetUserName();    }

public class UserService：IUserService    {        public string GetUserName()        {            return "张三";        }    }

在上面的ConfigureContainer方法把UserService注入进来，默认是瞬时注入

瞬时注入：containerBuilder.RegisterType().As().InstancePerDependency();;

单例注入：containerBuilder.RegisterType().As().SingleInstance();

生命周期注入：containerBuilder.RegisterType().As().InstancePerLifetimeScope();

注入试下是否注入成功

调用成功，证明注入成功

三、属性注入

1.把HomeController改成属性注入形式，属性注入有一个问题，就是那些属性需要注入？全部注入没必要，父类也有很多属性，要按需注入，给属性增加一个自定义特性标识说明需要注入。

public class HomeController : Controller    {        [AutowiredProperty]        private IUserService userService { get; set; }        public IActionResult Index()        {            string name = userService.GetUserName();              return View();        }    }

2.新增自定义特性类AutowiredPropertyAttribute.cs

[AttributeUsage(AttributeTargets.Property)]//为了支持属性注入，只能打到属性上    public class AutowiredPropertyAttribute: Attribute    {    }

3.增加识别特性类AutowiredPropertySelector.cs

public class AutowiredPropertySelector : IPropertySelector    {        public bool InjectProperty(PropertyInfo propertyInfo, object instance)        {            //判断属性的特性是否包含自定义的属性,标记有返回true            return propertyInfo.CustomAttributes.Any(s => s.AttributeType == typeof(AutowiredPropertyAttribute));        }    }

4.因为Controller 默认是由 Mvc 模块管理的，需要把控制器放到IOC容器中，在Program.cs中增加

//让控制器实例由容器创建builder.Services.Replace(ServiceDescriptor.Transient());

5.把容器注册到IOC容器，在Program.cs的ConfigureContainer()增加

//获取所有控制器类型并使用属性注入    Type[] controllersTypeAssembly = typeof(Program).Assembly.GetExportedTypes()        .Where(type => typeof(ControllerBase).IsAssignableFrom(type)).ToArray();    containerBuilder.RegisterTypes(controllersTypeAssembly).PropertiesAutowired(new AutowiredPropertySelector());

验证：

成功。

四、批量注入

实际项目中那么多需要注入的类，一个个写注册就不太现实了，需要一个可以批量注入的方法。

1.新建三个空接口IScopeDenpendency.cs，ISingletonDenpendency.cs，ITransitDenpendency.cs

/// 
    /// 瞬时注入    /// 
    public interface ITransitDenpendency    {    }　　/// 
    /// 单例注入标识    /// 
    public interface ISingletonDenpendency    {    }　　 /// 
    /// 生命周期注入标识    /// 
    public interface IScopeDenpendency    {    }

2.把上面要注入的类实现上面的接口

3.新增一个IocManager类

/// 
    /// Ioc管理    /// 
    public static class IocManager    {        /// 
        /// 批量注入扩展        /// 
        ///         ///         public static void BatchAutowired(this ContainerBuilder builder, Assembly assembly)        {            var transientType = typeof(ITransitDenpendency); //瞬时注入            var singletonType = typeof(ISingletonDenpendency); //单例注入            var scopeType = typeof(IScopeDenpendency); //单例注入            //瞬时注入            builder.RegisterAssemblyTypes(assembly).Where(t => t.IsClass && !t.IsAbstract && t.GetInterfaces().Contains(transientType))                .AsSelf()                .AsImplementedInterfaces()                .InstancePerDependency()                .PropertiesAutowired(new AutowiredPropertySelector());            //单例注入            builder.RegisterAssemblyTypes(assembly).Where(t => t.IsClass && !t.IsAbstract && t.GetInterfaces().Contains(singletonType))               .AsSelf()               .AsImplementedInterfaces()               .SingleInstance()               .PropertiesAutowired(new AutowiredPropertySelector());            //生命周期注入            builder.RegisterAssemblyTypes(assembly).Where(t => t.IsClass && !t.IsAbstract && t.GetInterfaces().Contains(scopeType))               .AsSelf()               .AsImplementedInterfaces()               .InstancePerLifetimeScope()               .PropertiesAutowired(new AutowiredPropertySelector());        }

4.把注入类ConfigureContainer改成

5.防止Program.cs代码过多，建一个Module把注入代码搬走，新建AutofacRegisterModule.cs类把ConfigureContainer的代码移过去

public class AutofacRegisterModule : Autofac.Module    {        protected override void Load(ContainerBuilder builder)        {            //获取所有控制器类型并使用属性注入            Type[] controllersTypeAssembly = typeof(Program).Assembly.GetExportedTypes()                .Where(type => typeof(ControllerBase).IsAssignableFrom(type)).ToArray();            builder.RegisterTypes(controllersTypeAssembly).PropertiesAutowired(new AutowiredPropertySelector());            //批量自动注入,把需要注入层的程序集传参数,注入Service层的类            builder.BatchAutowired(typeof(UserService).Assembly);            //注入其它层的containerBuilder.BatchAutowired(typeof(其它层的任务一个类).Assembly);        }    }

ConfigureContainer的代码变成

五、手动获取实例

手动获取实例的场景有静态帮助类中获取实例，例如redisHelper中获取注入的配置文件中的连接字符串

1.在上面的IocManager类中增加

private static object obj = new object(); private static ILifetimeScope _container { get; set; }  public static void InitContainer(ILifetimeScope container)        {            //防止过程中方法被调用_container发生改变            if (_container == null)            {                lock (obj)                {                    if (_container == null)                    {                        _container = container;                    }                }            }        }        /// 
        /// 手动获取实例        /// 
        ///         ///         public static T Resolve()        {            return _container.Resolve();        }

2.在Program.cs中增加

3.验证，新建一个DataHelper.cs类

public class DataHelper    {        //手动注入UserService        private static IUserService userService = IocManager.Resolve();        public static string GetData()        {            return userService.GetUserName();        }    }

成功获取到值，证明从容器中获取成功。

六、其它用法1.不用接口，直接注入实例

public class UserService :ITransitDenpendency    {        public string GetUserName()        {            return "张三";        }    }

2.一接口多实现

public class UserService :IUserService    {        public string GetUserName()        {            return "张三";        }    } public class UserService2 : IUserService    {        public string GetUserName()        {            return "张三2号";        }    }

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