real-world entity framework

Real-world Entity Framework

Llewellyn Falco – A Developer’s DeveloperLynn Langit – A DBA and more

Agenda

QueryQuery

SaveSave

PatternsPatterns

What is Entity Framework 4?

Object Relational Mapper (ORM)•Included in .NET 4.0•Developers write .NET code

• using LINQ • generate database access

code

DEMO - startING with EFGenerating a Model

What did we just do?

• Created a new project in Visual Studio• Added a new ADO.NET Entity Model • Generated a model from a database• Reviewed the generated model

diagram• Created an ObjectContext

Programmatically access data by…

ADO.NET

• Custom DAO• T-SQL

Entity Framework

• Complete DAO• LINQ

Agenda

QueryQuery

Real-World Problem #1 - Report

• Report for customer ‘Lynn’• Sent orders

# 54, #63, #57

• Partially sent orders #82: awaiting shoes, pants #92: awaiting gloves

• Unshipped orders #93 6 items #97 5 items

The Report T-SQL

Code DemoCurrent Practices- Life without Entity Framework

Code DemoReport with Entity Framework

Using EF – Writing a Query using LINQ

Compare Extracting Data

Mapping Relationships

CustomerIdName

CustomerIdName

Id Name Id Number Total Customerid

ADO.Net

InvoiceIdNumberTotalCustomerId

InvoiceIdNumberTotalCustomerId

CustomerIdName

CustomerIdName

InvoiceIdNumberTotalCustomerId

InvoiceIdNumberTotalCustomerId

EF

Code Demo - ContinuedReport with Entity Framework

Smart Objects

InvoiceIsShippedIsUnshippedIsPartiallyShiped

InvoiceIsShippedIsUnshippedIsPartiallyShiped

CustomerGetShippedGetUnshippedGetPartiallyShiped

CustomerGetShippedGetUnshippedGetPartiallyShiped

Looking at the T-SQL Generated by EF

• Use SQL Profiler• Create a trace• Filter for

Application:• EntityFramework

The N+1 Problem

1 + 1 + 5 = 7Customer Customers

InvoicesInvoices

ItemsTrips to

Database

More about Loading – Why Lazy Loading

• Lazy is Good and Easy, but

Lazy isn’t always efficient Lazy is always correct Sometimes better to use selective eager loading

• Syntax – use .Include("invoices.invoiceItems”)• More about – lazy loading - here

Code DemoConstrained Eager Loading

Agenda

SaveSave

Real-world Problem #2 – CRUD operations

WarehouseReport

Process Shipment

Load / Create Customer

Load / Create Invoice

Load / Create Invoice Item

Action

Remove Item

Set Item Shipped

ShippedCancelled

Code Demo

Warehouse

Processing

Using EF – Adding Data using LINQ

With Entity Framework…

• Simplified/ Reduced data access code Save Encapsulates

Delete Insert Update Key relationship Order of operations Transactions

• Prevents Most SQL Injection Sanitizes database inputs

SQL Injection and Entity Framework

“Little Bobby Tables”

Agenda

Patterns

Data Usage Patterns Load Model

Save Model

Manipulate Model

CommonPreferred

Code DemoModularity

Making Entity Framework Testable

Old Way

DoSomething()1)Get Data2)Manipulate Data3)Render Data

DoSomething()1)Get Data2)Manipulate Data3)Render Data

DoSomething()1)Load Data2)DoSomething(Data)

DoSomething()1)Load Data2)DoSomething(Data)

DoSomething(Data)1)Manipulate Data2)Render Data

DoSomething(Data)1)Manipulate Data2)Render Data

Load()1)Get DataLoad()1)Get Data

New Way - Testable

Code DemoTesting Loaders

MyProject.ControllerMyProject.Controller

MyProject.BusinessMyProject.Business

MyProject.ViewsMyProject.Views

MyProject.RulesMyProject.Rules

MyProject.ProcessesMyProject.Processes

Common Usage Pattern

Load Model

Save Model

Manipulate Model

Common Usage Pattern

MyProject.ControllerMyProject.Controller

MyProject.BusinessMyProject.Business

MyProject.ViewsMyProject.Views

MyProject.RulesMyProject.Rules

MyProject.ProcessesMyProject.ProcessesMyProject.LoadersMyProject.Loaders

Load Model

Save Model

Manipulate Model

Stored Procedures

• Security• Reduced Access• Performance• Modularity• Containment• Maintainability

Mapping Stored Procedures to EF Models

ORM to DB should be 1-1

• Complex mappings obscure the database

?=

Existing Database Problems are

Amplified

• Primary Keys• Wide Tables• Bad Names• Dead Columns

“Next Steps” for Attendees

• Use Entity Framework Write less CRUD code Protect against SQL Injection Master LINQ

• Use patterns / best practices with EF i.e. Loader pattern Modularity for testability (mocking)

• Map EF as closely as possible to the database Map 1-to-1 Fix design issues at the database level first

More about learning LINQ – using Koans

• 28 progressive examples to help you learn LINQ• LinqKoans.codeplex.com

Resources for Attendees

• EF team blog – here

• Julie Lehrman book - here

• Testing EF – video coming soon

On ApprovalTests YouTube playlist - here

www.ApprovalTests.com

Related Session(s)

http://www.devteach.com/Schedule.aspx •SQL361 - Query Tuning Tips for SQL Server

TeachingKidsProgramming.org

Do a Recipe Teach a Kid (Ages 10 ++)SmallBasic or Java Free Courseware (recipes)

Contact Information

@LlewellynFalco@LlewellynFalcowww.ApprovalTests.comwww.ApprovalTests.com

@LynnLangit@LynnLangitwww.LynnLangit.comwww.LynnLangit.com