This document provides an overview and demonstration of ASP.NET MVC and Entity Framework. It introduces the speaker and agenda, which includes an overview of MVC and EF concepts like models, views, controllers, and entity relationships. It then demonstrates how to add an Entity Data Model to a project and use EF features like lazy loading, eager loading, contexts, and basic CRUD operations with LINQ queries. Finally, it discusses using repositories to encapsulate data access code.

1. ASP.NET MVC and Entity Framework
SoCal Code Camp
Saturday, October 23, 2010
James Johnson
Technical Evangelist

2. • 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?

3. • 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

4. Demo

5. • 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

6. • 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

7. • 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

8. • 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 Framework
Definitions

9. Adding an EDM to your project
Demo

10. • 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 Framework
Lazy Loading

11. 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 Framework
Eager Loading

12. • 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 Framework
Contexts

13. Entity Framework
Contexts
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();

14. Entity Framework
Contexts
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();
}

15. • Very similar to LINQ to SQL
• Major difference
• LINQ to SQL - .SingleOrDefault()
• LINQ to Entities - .FirstOrDefault()
Selecting
public Course GetCourse(int id)
{
var course = (from c in _db.Courses
where c.Id.Equals(id)
select c).FirstOrDefault();
return course;
}
Entity Framework
LINQ to Entities

16. Deleting
public 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 Framework
LINQ to Entities

17. 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 Framework
LINQ to Entities

18. • 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

19. Repositories
• Add the two projects to your solution
• Add references to your project

20. using GenericRepository
public class MyController
{
private readonly IGenericRepository _repo;
private readonly CourseEntities _db;
public MyController()
{
_repo = new EFGenericRepository.EFGenericRepository(_db);
}
}
Repositories

21. // 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

22. Questions?

23. James Johnson
jamesj@componentone.com
www.latringo.me
www.speakerrate.com/latringo
Twitter, @latringo
Inland Empire .NET User’s Group
www.iedotnetug.org
2nd Tuesday’s of each month in Riverside, CA
Thank you