autofac(1)转

AutoFac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

    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

　　 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

    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

    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

    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。

    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：

    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

    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

    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。

    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

    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

    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

    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);
    }