ASP.NET MVC and Entity FrameworkUtah Code Camp

Saturday, September 25, 2010James Johnson

Technical Evangelist

Technical Evangelist with ComponentOne Founder and President of the Inland

Empire .NET User’s Group Microsoft MVP

But I don’t consider myself an expert. I just love to play

ADHD/ADD/OCD when it comes to new technology

Can’t stay away from the shiny new stuff Please don’t drop any new coins during the

presentation

Who am I?

Overview of ASP.NET MVC Overview of Entity Framework

Things that are cool Things to watch out for How to do it

Agenda

Demo

Models Views Controllers No Postbacks Very limited use of existing server controls Clean HTML makes CSS and JavaScript easier What all the cool kids are using these days.

ASP.NET MVC

First version (V 1) came with .NET 3.5 SP1 August 2008 Not widely thought of by the community

Second version (V4) released with .NET 4 Maps POCO objects to Database objects A collection of things instead of a dataset of

rows “things” are the Entities

Entity Framework

Why? Adds a layer of abstraction between Database

and Code DBA can structure DB how they want Developer can map to the DB how they want

Rename Entities for more comfortable use. EF handles the mapping

Entity Framework

Entity Data Model – EDM Deals with the Entities and the Relationships

they use Entities

Instance of EntityType Represent individual instances of the objects

Customer, books, shoes Fully typed

Relationships V1 was difficult to work with relationships

Needed special tricks to load related data

Entity FrameworkDefinitions

Adding an EDM to your project

Demo

A design pattern to defer initialization until needed.

EF 4 fixes a lot of problems with thisSupports Lazy LoadingOFF by defaultObjectContext setting, not application setting

context.ContextOptions.DeferredLoadingEnabled=true;

List<Thing> things = context.Things.ToList();foreach(var thing in things){

var thingItems = thing.ThingItems}

Entity FrameworkLazy Loading

Use if you will be needing every related entity

List<Thing> things = context.Things.Include(“ThingItems”);

foreach(var thing in things){

var thingItems = thing.ThingItems}

Entity FrameworkEager Loading

The context is the instance of the entity Passing an entity around to tiers breaks the

context V4 handles this issue with “self-tracking”

entities Make sure the context is always the same

Entity FrameworkContexts

Entity FrameworkContexts

public class ModelHelper { private static CourseEntities _db; public static CourseEntities CourseEntities { get { if(_db == null) _db = new CourseEntities(); return _db; } set { _db = value; } } }

private readonly CourseEntities _db = new CourseEntities();

Entity FrameworkContexts

private Student AddStudent(Student student, Course course){

student.Courses.Add(course);_db.SaveChanges();

}

Didn’t work because course was in a different context

private Student AddStudent(Student student, Course course){

var newStudent = GetStudent(student.Id);var newCourse = GetCourse(course.Id);newStudent.Courses.Add(newCourse);_db.SaveChanges();

}

Very similar to LINQ to SQL Major difference

LINQ to SQL - .SingleOrDefault() LINQ to Entities - .FirstOrDefault()

Selectingpublic Course GetCourse(int id){ var course = (from c in _db.Courses where c.Id.Equals(id) select c).FirstOrDefault(); return course;}

Entity FrameworkLINQ to Entities

Deletingpublic void DeleteCourse(Course course){

_db.DeleteObject(course); _db.SaveChanges();}

Adding (Inserting)public void AddCourse(Course course){ _db.AddToCourses(course); //this will be a list of AddToX _db.SaveChanges();}

Entity FrameworkLINQ to Entities

Editing (Updating)public void EditCourse(Course course){

_db.Courses.Attach(new Course { Id = course.Id }); _db.Courses.ApplyCurrentValues(course); _db.SaveChanges();}

“course” has been edited somewhere else – MVC Controller, so a “stand-in” is created

Entity FrameworkLINQ to Entities

Questions?

Tweet “@componentone <3’s Utah Code Camp” for a second chance to win

James Johnsonjamesj@componentone.comwww.latringo.meTwitter, @latringo

Inland Empire .NET User’s Groupwww.iedotnetug.org2nd Tuesday’s of each month in Riverside

Thank you