Asp.Net Mvc Design Pattern

INTRODUCTION TO DESIGN PATTERN O C O O S G A ASP.NET MVC Jaffal Hasan November 2009

AGENDA Design Patterns Overview MVC Design Pattern MVC vs. ASP.NET Layered Application Example MVC vs. Layered Application

DESIGN PATTERN OVERVIEW Set of guidelines Provide solutions to common software design problems bl Consists of one or several software design elements such as modules, interfaces, classes, objects, methods, functions, processes, threads, etc., Relationships among the elements, and a behavioral description Example design patterns: Model/View/Controller

DESIGN PATTERN OVERVIEW Advantages: Improve the structure of software Simplify Si lif maintenance i t Shared language for communicating Separation of concerns Minimize logic needed in views Enhance testability Reduce development time Easy to customize applications Disadvantages: Design pattern can be overkill in Simple UI

GOALS • Separation of concerns • Decoupling the layers and components • R d i Reducing d development time ( multi processes at time) l i li i ) • Testability • Flexibility Fl ibilit • Minimal Code in UI • Changes in layers: DBMS • Change or use multiple platform to present data (mobile – web ..)

WHAT IS ASP.NET MVC? A new Web Application Project type Simply an option Not N a replacement for W bF l f WebForms Builds on top ASP.NET Manual vs. Automatic Transmission Existing ASP.NET features such as master pages, web controls, validation, membership integrated.

WHAT MVC IS NOT ? Not the new Web Forms 4.0 Not replacing Web Forms, but Adds to it Not a whole new engine but sits on ASP.NET engine

WHAT MVC IS? Maintain Clean Separation of Concerns Extensible and Pluggable Great integration within ASP.NET

MVC Model View Controller • All b i business • UI • H dl and Handles d logic response user • ADO.NET, interaction Linq, Linq to • Work with SQL model to retreive information and select view to render with model data • Input logic p og c

MVC Model

MVC FLOW

MVC FLOW Controller Request Step 1 Incoming request directed to Controller

MVC FLOW Controller Model Step 2 Controller processes request and forms a data Model

MVC FLOW Controller Vi View Step 3 Model is passed to View

MVC FLOW Controller View Step 4 View transforms Model into appropriate output format

MVC FLOW Controller View Response Step 5 Response is rendered

MVC : MODEL – VIEW - CONTROLLER

REQUEST FLOW –DETAILED Request HTTP Http Routing Controller Response Handler Route View Route View Handler Engine

MVC VS. “CLASSIC” ASP.NET Classic ASP.NET MVC Framework Request Data Request Data Code Postback behind REST MVC

MVC VS. “CLASSIC” ASP.NET MVC is based on ASP.NET framework i b d ASP NET f k REST model versus the postback model of classic ASP.NET. Each page is split into two distinct components - controller and view - that operate over the same model of data. This is opposed to the classic code-behind model where no barrier is set that forces you to think in terms of separation of concerns and controllers and views. A good developer could achieve separation of concerns even without adopting MVC and its overhead. p g MVC is a model superior to a properly-done code- behind for its inherent support for test-driven development. p

REST ? Set of guidelines REST is an architectural pattern that defines how network resources should be defined and addressed in order to gain shorter response times, clear separation of concerns between the y front-end and back-end of a networked system

WHAT? NO MORE POSTBACKS! The MVC Framework Doesn't support classic postbacks and viewstate Doesn't consider any URL as th endpoint to a D 't id the d i t t physical server file to parse and compile to a class. In ASP.NET, you have a 1:1 correspondence between a URL and a resource.

WHY MVC? Very Clean separation of Concerns Unit Testing Model that leads you down a maintainable path (prevent spaghetti code) Clean URL and HTML Cl URLs d

CLEAN URL Url no longer points to the view/aspx page A Url maps to a controller class Allows more flexibility to map Urls Url routing engine, Route table www.arabiagis.com/software/powermap Or www.arabiagis.com/software.aspx?id=23

ROUTING ENGINE URLs -> application -> Controller Action Construct outgoing URLs Constructed URLs can be used to call back to Controllers/Actions

LAYERED APPLICATIONS SOUNDS GOOD Layered application design concept sounds good, but the problem is when it's time to code it. Let’s See L t’ S an example l Presentation Layer aye BLL DAL

AL THEYAB FLIGHTAVAILABILITY.ASPX RE-VISIT Is the code Maintainable ? Testable T t bl ? Are the object serializable ? The presentation layer can be simply tested and changed? Can we display the same data using a platform other than the webforms? Where is the separation of concerns? Presentation – Business Logic g

WHO’S RESPONSIBLE? The Coder? The Developer ? The Designer? All of them: The designer should put clear and clean guidelines! The coder should follow the guidelines and rules The d Th developer should d his work: think before l h ld do hi k thi k b f coding.

WHO’S RESPONSIBLE? Many developers can argue that they are doing a layered application, but they are writing all the logic in the code b hi d fil of a f h d behind file f form. Or Some of Developers try to separate the business logic and D l t t t th b i l i d the data layers. Everyone h different ideas and experiences E has diff t id d i about doing this. So even when layers have a defined responsibility its necessary to restrict the way the application is actually coded. And the only way to do that is y y y applying a design that affects the code structure.

BEST CHOICE MVC Layered Application 1. 1 Guidelines and Rules 1. 1 Developer decides 2. Shared language for 2. Every team member communicating speaks a language p g g 3. Easy to maintain 3. Hard to maintain 4. Ambiguous and 4. 4 Easy to understand variant structure the structure 5. Application is 5. 5 The code depends of dependent of the the developer skills developer skills and and opinions opinions

Practical “You should be pragmatic with any pattern, it's not necessary to be applicable for every situation” Jaffal Hasan THANKS FOR LISTENING. Mail: hjaffal@arabiagis.com LinkedIn profile: http://www linkedin com/in/jaffal http://www.linkedin.com/in/jaffal Blog: www.solutionsarchitecture.wordpress.com

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Asp.Net Mvc Design Pattern

by Hasan Jaffal on Nov 12, 2009

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