ASP.NET MVC and Entity FrameworkDesert Code Camp

Saturday, November 13, 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• Basic MVC Application• Models, Views, Controls, Helpers

• Overview of Entity Framework• Things that are cool• Things to watch out for• How to do it

Agenda

Demo

• Models• Views• Controllers• No Post backs• 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 this• Supports Lazy Loading• OFF by default• ObjectContext 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

• Repository pattern encapsulates code into a separate class

• Allows for easy changes• Can use it to switch database providers or new

technologies• Stephen Walther – ASP.NET MVC Framework, Sams• stephenwalther.com• “Download the code” link

Repositories

Repositories

• Add the two projects to your solution• Add references to your project

using GenericRepositorypublic class MyController{ private readonly IGenericRepository _repo; private readonly CourseEntities _db;

public MyController() { _repo = new EFGenericRepository.EFGenericRepository(_db); }}

Repositories

// get _repo.Get<Course>(id);

// edit _repo.Edit(course);

// create _repo.Create(course);

// delete _repo.Delete(course);

// list var list = _repo.List<Course>().Where(x => x.CourseName.Contains());

Repositories

Questions?

James Johnsonjamesj@componentone.comhttp://c1.ms/latringowww.speakerrate.com/latringohttp://bit.ly/latringo_dccTwitter, @latringo

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

Thank you