Entity Framework

Agenda

● ORM

● EF Modelling

● LINQ

● EF Inheritance

● EF Concurrency

Why Database Layer

Object Impedance Mismatch - RDBMS and OOP

Object 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 Support

Single RDBMS Support to Various RDBMS Support

DB Layer Uniformity Across the Organization

Entity Framework - Roadmap

EF - Key Terms

Entity

Context - Object Context, Db Context

Deferred Execution

POCO - Plain Old CLR Object

LINQ to Entities, Entity SQL

Mapping, Conceptual Model, Storage Model

Projections

EF - Resultant Objects

IEnumerable vs IQueryable

EF - Loading

Lazy, Eager Loading and Explicit Loading

Loading Navigation Properties

1. LazyLoadingEnabled = true

2. 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 Designer

Classes auto-generated from model

Preferred approach for existing database

Hands On

Database First - Tables, Stored Procedures, Views, Functions

Update Model

Modelling - Model First

Create model in EF Designer

Generate database from model

Classes auto-generated from model

Preferred approach for new database.

Hands On

Model First - Create Model, Generate Database

Update Model

Modelling - Code First

Define classes and mapping in code

Database created from code

Migrations apply model changes to database

Preferred 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 only

Database Generation

Database 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, Ordering

Joining

Grouping

EF - LINQ - Filtering, Ordering

EF - LINQ - Joining

EF - LINQ - Grouping

Homework

Full Outer Join Possible?

Use of “let” variable

EF - Code First

Conventions

Data Annotations

FluentApi

EF - Code First - Conventions

Convention: Table Name

Default: Entity + s (e.g Users)

Convention: Primary Key

Default: Id

Convention: Foreign Key Relation

Default: 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 entities

Executing 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 Configuration

Gives 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 Configuration

Retrieval 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 Configuration

Properties 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 One

One to Many

Many to Many

EF - Relationships - One to One

EF - Relationships - One to Many

EF - Relationships - Many to Many

Hands On

One to One

One to Many

Many to Many

EF - Concurrency

Optimistic

Pessimistic

EF - Concurrency - Optimistic

None: Default and there is no concurrency

Fixed: Original value of concurrency column is included in where part while generating SQL

Rows are not locked. Read operation can be never locked

EF - Concurrency - Optimistic

Sample Code

EF - Concurrency - Pessimistic

Involves database locking operations. So it is slow

Use Transaction to achieve it

Read 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