AutoFac使用方法总结一：注册

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);
     }

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