C# 4 and .NET 4

1260 ❘ ChaPTer 42 Asp.net dynAmic dAtA And mvc
What is mVC
MVC is a way of programming that involves breaking your code into three distinct parts: models, views,
and controllers. This is not a web-specific idea, and can be applied to any system that involves user
interaction. The definition of these terms is as follows:
➤
➤
➤
Model — A model refers to code that represents the data or state of an application. Note that this
doesn’t include data storage, which if included is the job of, for example, a database. However, it does
encapsulate all manipulation of data, including business logic such as validation rules. It also includes
the code necessary to interact with the underlying data store, if one exists.
View — A view is the user interface that exposes the model to the user and allows the user to perform
operations on the model. There is not necessarily a one-to-one relationship between views and models;
a given model may be visualized through multiple views. Any changes to models should be reflected
through changes in any associated views.
Controller — Controllers are responsible for mediating between models and views. When the user
performs an action on a view, the controller responds to the action and, if necessary, forwards the
action on to the model by interacting with it directly.
The relationship between these three parts are shown in Figure 42-8.
The controller has access to both the view and the model, as it must
mediate between them. The view must render information from and
reflect changes in the model, so it also requires access to the model.
There are numerous advantages to programming in this way. First,
and most obviously, it provides a clean separation of functionality
figure 42-8
between distinct units of an application. These may even be developed
independently, assuming that well-defined contracts exist between the parts. This means that MVC
applications are perfect in situations where a large team of developers works on a project simultaneously.
Another advantage that follows on from this is that unit testing becomes much easier, as each part can be
unit tested independently when required. Applications with user interfaces are notoriously difficult to test,
as it is often difficult or impossible to design tests that precisely mimic what a user will do, and automation
of a user interface can be a major challenge. Since MVC defines exactly what actions a user may perform via
controllers, you can be sure that if those controllers are tested adequately you won’t run into any surprises.
After all, the view can only interact with the controller in the same way as any other client code can interact
with the controller, including test code.
The main disadvantage of MVC is that there is an increase in complexity and, potentially, more code to be
written. For small-scale applications, this may not be desirable, and it certainly will increase development
time. It may also make it more difficult to make use of all the features provided by the overarching
technology being used for the application. For example, when this technology is used with ASP.NET,
as you will see, event-based user interaction and view state are not usable.
What is asP.neT mVC
Model
ASP.NET MVC applies the principles of MVC to the ASP.NET development environment. This means
that ASP.NET pages and controls are used as views, .NET classes are used for controllers, and a data
framework such as LINQ to SQL or the ADO.NET Entity Framework is used for the model.
You could, if you wanted, stop reading right now and start writing MVC web sites using ASP.NET.
However, what is particularly exciting with .NET 4 is that a full implementation of the MVC pattern is
included for you, with plenty of supporting classes that handle a lot of the plumbing (to connect things) and
scaffolding (to reduce repetitive or boilerplate code) for you. This is the ASP.NET MVC 2 Framework.
The best way to see what is on offer here is to dive straight in and build an application (or inspect the
version in the downloadable code for this chapter).
View
Controller
www.it-ebooks.info