[MVCSharp]MVC# Overview概述

MVC# Overview概述

Abstract: This article gives an overview of MVC# - a Model-View-Presenter framework for .NET platform. It firstly explains the MVP pattern essentials and then walks through the key features of the MVC# framework which help building true MVP-based solutions.

MVC#概述，.Net平台的MVP框架。首先介绍MVP模式的必要性，接着简要介绍MVC#的关键要素，助力基于MVP模式的解决方案构建。

What is Model-View-Presenter? 什么是MVP
    3-tier architecture 三层架构
    MVC and MVP patternsMVC和MVP
Why using MVC#? 如何使用MVC#
    1. Views and controllers get connected automatically 视图和控制器自动连接
    2. Multiple GUI platforms supported 多种GUI平台支持
    3. Platform-independent navigation to views 平台独立的视图导航
    4. Tasks concept 任务的概念
Conclusion 结论

What is Model-View-Presenter?什么是MVP？

3-tier architecture三层架构

One of the most fundamental approaches in software engineering is the Layered architecture. It implies dividing a system into several interacting layers with certain limitations imposed on how layers may interact.s Layered architecture finds its application in various systems for example net protocols (TCP/IP layers), operating systems (three layers: core, drivers, applications) and others.

软件工程中一个最重要的方法就是分层架构。

A particular case of layered architecture is the 3-tier architecture with its variations: Model-View-Controller and Model-View-Presenter. Before considering MVP (and MVC) let us discuss the general 3-tier architecture and its difference to the conventional programming style.

一个特别的架构模式就是三层架构和他的不同表现形式：MVC和MVP.在考虑MVP或者MVC之前我们先讨论普通的三层架构和传统编程形式的区别。

A straightforward (and widely used) approach in designing applications is the 2-tier architecture. According to it an application consists of a presentation layer and a domain layer. Domain layer classes represent the problem domain entities (e.g. customer, order) and are usually bound to some database access facilities. Presentation classes in 2-tier architecture have the following responsibilities:

• receive user input接受用户输入
• make necessary calls to the domain tier 必要的调用
• decide what to show next to the user 确定下面展示给用户什么
• display output 显示输出

These responsibilities are rather vast and, as a system grows, may result in a bloated presentation layer. Moreover they logically can be divided into two groups: actually presentation logic (code for perceiving input and displaying output) and application logic (communication with the domain tier and application flow decisions). These responsibilities require different programming skills and should better be not mixed in a single module/class. A quite natural solution is to split this too broad presentation layer into two: presentation and application logic:

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3-tier architecture is rather abstract. While it declares an existence of three layers, it says nothing about classes in these layers and their interaction. A much more precise form have two 3-tier architecture variations: Model-View-Controller and Model-View-Presenter. Let us proceed to their discussion.

MVC and MVP patterns MVC和MVP模式

According to both MVC and MVP the presentation layer consists of view objects, and application logic consists of controller objects (we will use "controller" name instead of "presenter" in MVP). For each view object a corresponding controller exists and vice versa. And although MVC and MVP are based on a common 3-tier principle: views process only presentation needs and controllers handle application logic, these patterns have two major differences:

在MVC和MVP中表现层包括视图对象。应用层包括控制器对象（使用控制器代替表示器）。每个视图对象对应一个控制器。尽管MVC和MVP基于同样的三层准则：视图只负责表现，控制器处理应用逻辑，这两个模式有两个主要的区别：

1. In MVC controllers receive and process user input, but in MVP views receive user input and then merely delegate processing to the corresponding controllers. That is why MVP pattern better fits modern UI environments (Windows/Web forms) where view classes themselves handle user gestures.

在MVC中控制器接收和处理用户输入，在MVP中视图接受用户输入接着委托给相应的控制器处理。这是为什么MVP模式更适合现在的UI环境（Window/Web Forms），视图类自身处理用户的手势。

2. In MVC controllers affect their views by changing the intermediate presentation model, which the views are subscribed to (by observer pattern). This makes views pure observers without direct access to them. MVP on the other hand violates this "pure observer" rule by providing a direct link from a controller to its view. This makes MVP more handy as compared to MVC.

在MVC中控制器影响他们的视图是通过直接改变视图订阅的表现层模型来实现的，这使得视图成为纯观察者而不能直接接触控制器。而另一方面，MVP则侵犯了纯观察者通过直接提供控制器的引用。这使得MVP比MVC更具处理性。

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The said differences make the MVP pattern more attractive than MVC from the developer‘s point of view. And indeed MVP was designed to be an evolution of MVC and to improve the latter. That is why we often refer to MVP as "sharp MVC" and therefore the name our MVP framework is MVC#.

所述的不同从观察者的角度使MVP比MVC更具吸引力。事实上MVP被设计来发展MVC。这使我们为啥称MVP为Sharp MVC 的原因，也是我们的MVP框架称为MVC# 的原因。

Why using MVC#?

Now that we are convinced in the usefulness of the MVP pattern we may start using it in our applications. However it may be not as easy. Maintaining an additional application logic layer may require considerable efforts. For example a developer needs to take care of linking between all views and appropriate controllers,

Fortunately MVC# automates and takes on itself much of the work concerned with MVP usage. Thus it simplifies and speeds up the development of MVP applications. Below is the list of MVC# framework features:

1. Views and controllers get connected automatically

Developers do not have to care about associating views with their controllers. MVC# framework automatically establishes links between views and corresponding controllers:

开发者不必关心视图和控制器的关联。MVC# 框架自动实现视图和相应的控制器的连接。

publicclass OrderDetailsView

    ...

    privatevoid processOrderButton_Click(object sender, EventArgs e)

    {

        // No code needed to establish a link to the controller

        (Controller as OrderDetailsController).ProcessOrder();

    }

2. Multiple GUI platforms supported

MVC# allows targeting different GUI platforms (Windows, Web, Silverlight, etc.) Thus the same application can be used with quite different presentation layers - one for Windows, the other for Silverlight or Web environment, etc.:

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3. Platform-independent navigation to views 平台无关导航到视图。

To make application logic fully independent of the presentation layer, MVC# provides a platform-independent way of navigating to views. Instead of  activating a Windows form or redirecting to a Web page a developer should simply call a uniform Navigator.Navigate(...) method:

为了使应用逻辑完全独立于表现层，MVC# 提供了一个平台无关的导航到视图的方法。无论是激活Windows窗体还是导航到WebPage只要通过调用Navigator.Navigate(...)方法。

publicclass OrderDetailsController

    ...

    publicvoid ProcessOrder()

    {

        // No Response.Redirect(...) or Form.Show() calls

        Task.Navigator.Navigate(OrderSupportTask.ProcessOrder);

    }

4. Tasks concept任务的概念

Another useful feature of MVC# framework, although not directly related to the MVP pattern, is the Task concept. A task unites several views with their controllers in fulfilling some job. For example a ticket booking task may consist of two views: one to choose a ticket, the other - to do the payment. In MVC# all controllers within a task are given a link to the task object. Generally a task can be expressed as a workflow or a state machine.

另外一个有用的MVC#元素是任务的概念，尽管不是直接关系到MVP模式。一个任务包括多个视图和它们的控制器来完成一些工作。例如购票任务可能包括两个视图，一个是选票，一个是付款。在MVC#，所有的在一个任务中的控制器，同时指向任务对象。一般地，一个任务可以被表述为一个工作流或者状态机。

Conclusion

MVC# framework frees developers from much of extra work required in construction of Model-View-Presenter applications. It allows creating flexible MVP-based application with almost no extra cost. For more information on MVC# including the examples of using it see the project web site.

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