Entity Framework

Agenda

● ORM● EF Modelling● LINQ● EF Inheritance● EF Concurrency

Why Database Layer

Object Impedance Mismatch - RDBMS and OOPObject Conversions - RDBMS to OOP and OOP to RDBMS

Needs Easy Conversion Process - Rise of ORM

ORM?

Many Frameworks - EF, NH, LINQ to SQL

RDBMS to NoSQL SupportSingle RDBMS Support to Various RDBMS Support

DB Layer Uniformity Across the Organization

Entity Framework - Roadmap

EF - Key Terms

EntityContext - Object Context, Db Context

Deferred Execution

POCO - Plain Old CLR Object

LINQ to Entities, Entity SQL

Mapping, Conceptual Model, Storage ModelProjections

EF - Resultant Objects

IEnumerable vs IQueryable

EF - Loading

Lazy, Eager Loading and Explicit Loading

Loading Navigation Properties1. LazyLoadingEnabled = true2. LazyLoadingEnabled = false & Include(“{Navigation Property}”) 3. LazyLoadingEnabled = false & {Navigation Property}.Load()

Modelling - .edmx

Modelling - .edmx - Types

Database First

Model First

Modelling - Database First

Reverse engineer model in EF DesignerClasses auto-generated from model

Preferred approach for existing database

Hands On

Database First - Tables, Stored Procedures, Views, FunctionsUpdate Model

Modelling - Model First

Create model in EF DesignerGenerate database from modelClasses auto-generated from model

Preferred approach for new database.

Hands On

Model First - Create Model, Generate DatabaseUpdate Model

Modelling - Code First

Define classes and mapping in codeDatabase created from codeMigrations apply model changes to databasePreferred approach for new database. Generally preferred in Agile/Scrum

Modelling - Fluent Api, Configuration and Conventions

Fluent Api - Chaining Api

Configuration with Fluent Api

Conventions

Hands On

Code First - Create Classes with Conventions onlyDatabase GenerationDatabase Migration

EF - CRUD

EF - Read Operation

EF - Create - Single Record

EF - Create - Multiple Records

EF - Update Record

EF - Delete Record

Homework

AddressBook - Design Db and Do CRUD operations on all entities

EF - LINQ

Filtering, OrderingJoiningGrouping

EF - LINQ - Filtering, Ordering

EF - LINQ - Joining

EF - LINQ - Grouping

Homework

Full Outer Join Possible?Use of “let” variable

EF - Code First

ConventionsData AnnotationsFluentApi

EF - Code First - Conventions

Convention: Table NameDefault: Entity + s (e.g Users)

Convention: Primary KeyDefault: Id

Convention: Foreign Key RelationDefault: Entity + Id (e.g SubscriptionId)

EF - Code First - Data Annotations

Annotation: Table=> Table(“{Name”})

Annotation: Key=> Key

Annotation: ForeignKey=> ForeignKey(“{Navigation Property”})=> ForeignKey(“{Property”})

EF - Code First - Fluent Api

Homework

AddressBook - Design Db and Do CRUD operations on all entitiesExecuting Raw SQL - Plain, Stored Procedures

EF - Inheritance Strategy - TPH

EF - Inheritance Strategy - TPH

Needs a column, discriminator, that will used to identify exact type.

Retrieving Type in TPH

Code First ConfigurationGives better performance but there are many duplicate data and nullable columns.

EF - Inheritance Strategy - TPT

EF - Inheritance Strategy - TPT

Each entity maps to table. So CUD operations are faster

Code First ConfigurationRetrieval is slower than TPH as it needs joins with base class/table.

EF - Inheritance Strategy - TPC

EF - Inheritance Strategy - TPC

Each concrete entity maps to table.

Code First ConfigurationProperties of abstract entity are combined with concrete entity and many data/columns duplications.

EDMX designer does not support this mapping. Manual modification is required.

EF - Relationships

One to OneOne to ManyMany to Many

EF - Relationships - One to One

EF - Relationships - One to Many

EF - Relationships - Many to Many

Hands On

One to OneOne to ManyMany to Many

EF - Concurrency

OptimisticPessimistic

EF - Concurrency - Optimistic

None: Default and there is no concurrencyFixed: Original value of concurrency column is included in where part while generating SQLRows are not locked. Read operation can be never locked

EF - Concurrency - Optimistic

Sample Code

EF - Concurrency - Pessimistic

Involves database locking operations. So it is slowUse Transaction to achieve itRead operation can be locked

Questions

Thank you

EF - Advance

Table Splitting

After little bit experience, it is worth

Bounded Contexts

After little bit experience, it is worth

EF - Unit Testing

After little bit experience, it is worth

EF - Patterns

After little bit experience, it is worth