MVC and Entity Framework 4

ASP.NET MVC and Entity Framework
San Diego .NET User Group
Tuesday, March 23, 2010
James Johnson

Founder and President of the Inland Empire .NET User’s Group
Independent Consultant
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 shiny coins during the presentation
Who am I?

An effort to help support local user groups by providing speakers
Telerik speakers bureau

Overview of ASP.NET MVC
Overview of Entity Framework
Things that are cool
Things to watch out for
How to do it
Agenda

V 2.0 RTM’d March 11, 2010
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

Hey! There’s a big honking server control there!
Using the TelerikRadEditor in this project
Very easy to setup if you follow these rules
Needs to be in a “form” tag, not Html.BeginForm()
Handlers need to be changed from .aspx to .axd
DialogHandlerUrl, SpellCheckChettings
Use a custom tools file
ASP.NET MVCTelerikRadEditor

Setting
<% RadEditor1.Content = Model.Description %>
Getting
Need to pass in the request and name of editor
ASP.NET MVCTelerikRadEditor Set and Get Content
varcontent = _radControlHelper.GetEditorContent(Request, “RadEditor1");
public string GetEditorContent(HttpRequestBase request, string editorId)
{
varrawContent = (from postedValue in request.Form.Keys.OfType<string>()
where postedValue.EndsWith(editorId)
select request.Form[postedValue]).FirstOrDefault();
return Telerik.Web.UI.Editor.ContentEncoder.Decode(rawContent);
}

First version (V 1) came with .NET 3.5 SP1
August 2008
Not widely thought of by the community
Second version (V4) is set to be 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)
{
varthingItems = 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)
{
varthingItems = thing.ThingItems
}
Entity FrameworkEager Loading

The context is the instance of the entity
Passing an entity around to tiers breaks the context
V4 will handle this issue with “self-tracking” entities
Make sure the context is always the same
Entity FrameworkContexts

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

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)
{
varnewStudent = GetStudent(student.Id);
varnewCourse = 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()
Selecting
public 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

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();
}

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

Questions?

James Johnson
james@iedotnetug.org
www.duringlunch.com
Twitter, @latringo
Inland Empire .NET User’s Group
www.iedotnetug.org
2nd Tuesday’s of each month in Riverside
Thank you

MVC and Entity Framework 4

by James Johnson on Mar 24, 2010

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