Enterprise Design Patterns IntroDesigning your app the correct way – SSW Module 1725

Module Overview1. Intro to Dependency Injection2. Intro to the Onion Architecture3. Intro to Enterprise Data

Accessa) Repository Patternb) Unit of Work Pattern

4. View Models

Are you using Dependency Injection? Tried it? Like it? Used it in a project?

Dependencies

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The answer:

Dependency InjectionLoosely coupled classes

Increased code reuse

Maintainable code

Testable methods

All dependencies are specified in one place

Class dependencies are clearly visible in the constructor

Lets look at the OrderProcessor. Spot the Code Smell ?

Look Mum. No Dependencies !

Are you using Dependency Injection? Tried it? Like it? Used for new project? Refactored existing

code? Implemented

everywhere?

Onion Architecture

Enterprise Data Access Patterns

The Provided Solution Structure

Our Solution Structure

Repository

Directly Accessing Data

Duplicated code / No code re-use

Hard to centralize data-related policies (i.e. caching)

Hard to write unit tests

IIS

Controller

EF DBContext

Database

No RepositoryDirect access to the databasefrom the controller

IIS

Controller

EF Repository: IRepository

Database

With RepositoryAbstraction layer between controller and database context. Unit tests can use a custom persistence later to facilitate testing

Test Project

Controller

Mock Repository : IRepository

Mock Persistenc

e

Use the Repository Pattern

Isolates the data layer better unit testing support

Centralised, consistent access rules, logic and caching

Maintainability improved code re-use

Readability e.g. GetTopSellingItemsByCategory – Simple method name, complex SQL Query

http://blog.damianbrady.com.au/2012/03/07/a-generic-crud-repository-for-entity-framework/http://rules.ssw.com.au/SoftwareDevelopment/RulestobetterArchitectureandCodeReview/Pages/RepositoryPattern.aspx

IIS

Controller

LEGACY DATABASE:

IRepository

Database

Use Repositories to abstract legacy data access

Test Project

Controller

Mock Repository : IRepository

Mock Persistenc

e

IIS

Controller

EF Repository: IRepository

Database

New Functionality

Repositories – Migrating to modern data access

Implementing the Repository Pattern with Code First

Repository Interfaces

Generic Repository - Overview

Generic Repository – Db Context

Generic Repository - Implementation

The Repositories

Repositories in the store controller

Unit of Work Coordinates multiple

repositories with a single db context

UOW.SaveChanges() commits the changes made to all of the repositories

IIS

Controller

Unit of Work

Database

Unit of WorkEnsures that multiple repositories share a single database context

Test Project

Controller

Mock Unit Of Work

Mock Persistenc

e

Repository

MockRepositor

yRepositor

yMock

Repository

DbContext

Implementing the Unit Of Work Pattern

Where Is My Context?

Where the Magic Happens…..Our Dependency Injection Container !

Implementing the Repository Pattern with EDMX

I Need Some Context

Code First Context vs Edmx Generated Context

Generating Entities In My Domain ProjectFrom the EDMX

Update the T4 template to point to the EDMX

DB First - Repository + Unit of Work Entity Framework 4 instructions: http://

blogs.msdn.com/b/adonet/archive/2009/05/21/poco-in-the-entity-framework-part-1-the-experience.aspx

View Models models that describe a view pass data from a controller to a view. provides a convenient way of

representing complex view data

Benefits of View Models Remove logic from your views – viewmodels are

easily unit tested Security – remove properties from models you

don’t want in the view Loose coupling –views are not coupled to the

domain DataAnnotations describe the model

Summary1. Intro to Dependency Injection2. Intro to the Onion Architecture3. Intro to Enterprise Data

Accessa) Repository Patternb) Unit of Work Pattern

4. View Models