Question

我有一个MVC应用程序，我正在实施CQRS，我将已保存的数据从读取数据分离到单独的接口。我正在使用构造函数注入将这些接口的具体实例注入Controller。对于构造函数注入，我使用的是Unity容器。见下面的例子

//The Employee controller 
public class EmployeeController : Controller
{
    IEmployeeRepository _Writer;

    IEmployeeQuery _Reader;

    //constructor injection
    public EmployeeController(IEmployeeRepository writer, IEmployeeQuery reader)
    {
        this._Writer = writer;
   this._Reader = reader;   

    }


    //To Do: constructor injection for write operations only
    public EmployeeController(IEmployeeRepository writer)
    {
        this._Writer = writer;

    }

    //To Do: constructor injection for read operations only
    public EmployeeController(IEmployeeQuery reader)
    {
        this._Reader = reader;

    }
}


//Registration of the concrete types in the unity container.
public static class Bootstrapper
{
    public static void ConfigureUnityContainer()
    {
        IUnityContainer container = new UnityContainer();

        container.RegisterType<IEmployeeRepository, EmployeeRepository>(new HttpContextLifetimeManager<IEmployeeRepository>());
        container.RegisterType<IEmployeeQuery, EmployeeQueries>(new HttpContextLifetimeManager<IEmployeeQuery>());
        ControllerBuilder.Current.SetControllerFactory(new UnityControllerFactory(container));
    }
}

//The derived Controller Factory for injection dependencies in the Controller constructor
public class UnityControllerFactory : DefaultControllerFactory
{
    IUnityContainer container;

    public UnityControllerFactory(IUnityContainer container)
    {
        this.container = container;
    }
    protected override IController GetControllerInstance(RequestContext requestContext, Type controllerType)
    {


        try
        {
            if (controllerType == null)
            {
                throw new ArgumentNullException("controllerType");
            }

            if (!typeof(IController).IsAssignableFrom(controllerType))
            {
                throw new ArgumentException(String.Format("Type requested is not a controller: {0}", controllerType.Name), "controllerType");
            }

            return container.Resolve(controllerType) as IController;





        }
        catch (Exception)
        {

            return null;
        }
    }
}

我已经发现，对于任何操作，我将获取数据或写入数据，但不是两者。在这种情况下，我需要有条件地调用控制器构造函数，具体取决于＆＃34; _Writer＆＃34;或＆＃34; _Reader＆＃34;我需要初始化。

如何做到这一点？

Answer 1

看起来你有一个控制器，你应该使用两个？如果您永远不需要能够同时阅读和写作，我会考虑将该组件重构为单一责任。

如果您不想这样做，我会考虑注入NullObject而不是根本不注入该依赖项。请参阅this thread。

TecX project包含一个模仿NInject上下文绑定的扩展。这将允许您指定何时注入什么依赖项。代码可以在 TecX.Unity 项目（文件夹 ContextualBinding ）中找到。显示如何使用它的测试位于 TecX.Unity.ContextualBinding.Test 项目中。

Answer 2

延迟加载组件怎么样？您解决了两个依赖关系，但只初始化了一个真正使用的依赖关系。

此处示例：http://pwlodek.blogspot.com/2010/05/lazy-and-ienumerable-support-comes-to.html

MVC：有条件地调用重载的构造函数

2 个答案: