AutoFac使用方法总结:Part I

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

[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);
}

参考：http://niuyi.github.io/blog/2012/04/06/autofac-by-unit-test/