utoFac是.net平台下的IOC容器产品，它可以管理类之间的复杂的依赖关系。在使用方面主要是register和resolve两类操作。 这篇文章用单元测试的形式列举了AutoFac的常用使用方法：
注册部分
使用RegisterType进行注册
[Fact]public void can_resolve_myclass(){var builder = new ContainerBuilder();builder.RegisterType<MyClass>();IContainer container = builder.Build();var myClass = container.Resolve<MyClass>();Assert.NotNull(myClass);}
注册为接口
[Fact]public void register_as_interface(){var builder = new ContainerBuilder();builder.Register(c => new MyClass()).As<MyInterface>();IContainer container = builder.Build();Assert.NotNull(container.Resolve<MyInterface>());Assert.Throws(typeof (ComponentNotRegisteredException), () => container.Resolve<MyClass>());}
使用lambda表达式进行注册
[Fact]public void can_register_with_lambda(){var builder = new ContainerBuilder();builder.Register(c => new MyClass());IContainer container = builder.Build();var myClass = container.Resolve<MyClass>();Assert.NotNull(myClass);}
带构造参数的注册
[Fact]public void register_with_parameter(){var builder = new ContainerBuilder();builder.Register(c => new MyParameter());builder.Register(c => new MyClass(c.Resolve<MyParameter>()));IContainer container = builder.Build();Assert.NotNull(container.Resolve<MyClass>());}
带属性赋值的注册
[Fact]public void register_with_property(){var builder = new ContainerBuilder();builder.Register(c => new MyProperty());builder.Register(c => new MyClass(){Property = c.Resolve<MyProperty>()});IContainer container = builder.Build();var myClass = container.Resolve<MyClass>();Assert.NotNull(myClass);Assert.NotNull(myClass.Property);}
Autofac分离了类的创建和使用，这样可以根据输入参数（NamedParameter）动态的选择实现类。
[Fact]public void select_an_implementer_based_on_parameter_value(){var builder = new ContainerBuilder();builder.Register<IRepository>((c, p) =>{var type = p.Named<string>("type");if (type == "test"){return new TestRepository();}else{return new DbRepository();}}).As<IRepository>();IContainer container = builder.Build();var repository = container.Resolve<IRepository>(new NamedParameter("type", "test"));Assert.Equal(typeof(TestRepository),repository.GetType());}
AufoFac也可以用一个实例来注册，比如用在单例模式情况下：
[Fact]public void register_with_instance(){var builder = new ContainerBuilder();builder.RegisterInstance(MyInstance.Instance).ExternallyOwned();IContainer container = builder.Build();var myInstance1 = container.Resolve<MyInstance>();var myInstance2 = container.Resolve<MyInstance>();Assert.Equal(myInstance1,myInstance2);}
注册open generic类型
[Fact]public void register_open_generic(){var builder = new ContainerBuilder();builder.RegisterGeneric(typeof (MyList<>));IContainer container = builder.Build();var myIntList = container.Resolve<MyList<int>>();Assert.NotNull(myIntList);var myStringList = container.Resolve<MyList<string>>();Assert.NotNull(myStringList);}
对于同一个接口，后面注册的实现会覆盖之前的实现
[Fact]public void register_order(){var containerBuilder = new ContainerBuilder();containerBuilder.RegisterType<DbRepository>().As<IRepository>();containerBuilder.RegisterType<TestRepository>().As<IRepository>();IContainer container = containerBuilder.Build();var repository = container.Resolve<IRepository>();Assert.Equal(typeof(TestRepository), repository.GetType());}
如果不想覆盖的话，可以用PreserveExistingDefaults，这样会保留原来注册的实现。
[Fact]public void register_order_defaults(){var containerBuilder = new ContainerBuilder();containerBuilder.RegisterType<DbRepository>().As<IRepository>();containerBuilder.RegisterType<TestRepository>().As<IRepository>().PreserveExistingDefaults();IContainer container = containerBuilder.Build();var repository = container.Resolve<IRepository>();Assert.Equal(typeof (DbRepository), repository.GetType());}
可以用Name来区分不同的实现，代替As方法
[Fact]public void register_with_name(){var containerBuilder = new ContainerBuilder();containerBuilder.RegisterType<DbRepository>().Named<IRepository>("DB");containerBuilder.RegisterType<TestRepository>().Named<IRepository>("Test");IContainer container = containerBuilder.Build();var dbRepository = container.ResolveNamed<IRepository>("DB");var testRepository = container.ResolveNamed<IRepository>("Test");Assert.Equal(typeof(DbRepository), dbRepository.GetType());Assert.Equal(typeof(TestRepository), testRepository.GetType());}
如果一个类有多个构造函数的话，可以在注册时候选择不同的构造函数
[Fact]public void choose_constructors(){var builder = new ContainerBuilder();builder.RegisterType<MyParameter>();builder.RegisterType<MyClass>().UsingConstructor(typeof (MyParameter));IContainer container = builder.Build();var myClass = container.Resolve<MyClass>();Assert.NotNull(myClass);}
AutoFac可以注册一个Assemble下所有的类，当然，也可以根据类型进行筛选
[Fact]public void register_assembly(){var builder = new ContainerBuilder();builder.RegisterAssemblyTypes(Assembly.GetExecutingAssembly()).Where(t => t.Name.EndsWith("Repository")).AsImplementedInterfaces();IContainer container = builder.Build();var repository = container.Resolve<IRepository>();Assert.NotNull(repository);}
