Introduction to ASP.Net MVC

Points for discussion
•Introduction to Asp.NET MVC
•Architecture of Asp.NET MVC
•Model
•View
•Controller
•Goals of ASP.NET MVC
•File Structure
•Page Life Cycle
•Global.asax

Introducing ASP .NET MVC
• ASP .NET Web Controls have many benefits
• They allow web applications to be built rapidly
• They provide a very rich user experience
• They can easily be bound to data sources
• But there are many disadvantages
• As functionality increases so does the number of post-
backs
• The amount of View State data can grow alarmingly
• The underlying HTTP infrastructure is not hidden
• The most serious problems are architectural
• ASP .NET actively discourages MVC based best practices.

What is a Model?
•MVC model is basically a C# or VB.NET class
•A model is accessible by both controller and view
•A model can be used to pass data from Controller to
view
•A view can use model to display data in page

What is a View?
•View is an ASPX page without having a code behind
file
•All page specific HTML generation and formatting can
be done inside view
•One can use Inline code (server tags ) to develop
dynamic pages
•A request to view (ASPX page) can be made only from
a controller’s action method

What is a Controller?
•Controller is basically a C# or VB.NET class which
inherits System.Mvc.Controller
•Controller is a heart of the entire MVC architecture
•Inside Controller’s class action methods can be
implemented which are responsible for responding to
browser OR calling views.
•Controller can access and use Model class to pass data
to Views
•Controller uses ViewData to pass any data to View

Goals of ASP .NET MVC
•Enable proper unit and integration tests
• Controllers can be tested without the browser
• Data access layer can be ‘mocked out’
• Transparent naming conventions
• URL’s are simple and clean
•Take control over markup
•Build on top of ASP .NET infrastructure
• But make the post-back style controls optional

MVC File Structure & File Naming Standards

•MVC uses a standard directory structure and file naming standards
which are a very important part of MVC application development.
•Inside the ROOT directory of the application, there must be 3
directories each for model, view and Controller.
•Apart from 3 directories, there must have a Global.asax file in root
folder, and a web.config like a traditional ASP.NET application.

ASP.NET MVC Execution Life Cycle

Page Life Cycle
• The ‘UrlRoutingModule’ receives the request
•It creates and runs the correct ‘MvcHandler’
•The handler creates and runs a controller
•Creation is via the current ‘ControllerFactory’
•The entry point to the controller is ‘Execute’
•A ‘ControllerContext’ is passed as a parameter
•The controller runs the appropriate method
•This is found using standard reflection
•A list of parameters can be passed in
•Control is passed to the current ‘ViewEngine’
• Which (typically) builds and calls a server page

Global.asax
public class MvcApplication : System.Web.HttpApplication {
public static void RegisterRoutes(RouteCollection routes) {
routes.IgnoreRoute("{resource}.axd/{*pathInfo}");
routes.MapRoute(
"Default", // Route name
"{controller}/{action}/{id}", // URL with parameters
new { controller = "Home", action = "Index", id = "" }
);
}

protected void Application_Start() {
RegisterRoutes(RouteTable.Routes);
}
}

Passing Data Into The Server Page
• The simplest mechanism for passing data to the server
page is via the ‘ViewData’ object
•This is a dictionary that holds arbitrary objects
•The dictionary is populated in the controller and
automatically passed to the server page by the
‘MvcHandler’
•Information can be retrieved via a key or via generics
•E.g. ‘ViewData[“order”]’ or ViewData.Get<Order>()
•A more strongly typed solution is possible
•An arbitrary object is passed back from the controller
•The server page inherits from ‘ViewPage<T>’
•Where ‘T’ is set to the type returned from the
controller

Mixing MVC with Normal ASP .NET
•There is no problem combining MVC and Web Forms
•As everything is based on the same infrastructure
• An ASP .NET Web Application can contain:
•MVC based controllers, actions and views
•ASP .NET pages containing HTML and Web Controls
•Windows Communication Foundation based Web
Services
• Some changes may be required to routing tables
• MVC can be configured to ignore requests to existing
files
•But you may wish to add explicit exceptions to prevent
unnecessary calls which access the file system
•You can do this via ‘routes.IgnoreRoute(“...”)’

Using AJAX in Web Applications
•MVC uses jQuery to implement AJAX
•Using ‘Ajax.BeginForm()’ you can generate markup and
scripts that support partial post-backs
•It takes an ‘AjaxOptions’ parameter that holds the
ids of elements to be updated and where updates
should be placed
•This can be detected via ‘Request.IsMvcAjaxRequest’
•You then send changes via ‘return PartialView(...)’
•ASP .NET AJAX is not replaced
•It remains a better option for:
•Calling .NET based Web Services
•Creating client-side only controls
•Plus there is all the code in the control toolkit

Conclusion
• Uses MVC design pattern for separation of different
parts of the application
•More scalable
•More and easily extensible
•More testable for business logic.
•Supports EF like LINQ to SQL,ADO.NET EF Model,
Standard ADO.NET for readers and Datasets etc

Introduction to ASP.Net MVC

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