MVC and Entity Framework 4

ASP.NET MVC and Entity FrameworkSan Diego .NET User GroupTuesday, March 23, 2010James Johnson

Founder and President of the Inland Empire .NET User’s GroupIndependent ConsultantMicrosoft MVPBut I don’t consider myself an expert. I just love to playADHD/ADD/OCD when it comes to new technologyCan’t stay away from the shiny new stuffPlease don’t drop any shiny coins during the presentationWho am I?

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

Overview of ASP.NET MVCOverview of Entity FrameworkThings that are coolThings to watch out forHow to do itAgenda

V 2.0 RTM’d March 11, 2010ModelsViewsControllersNo PostbacksVery limited use of existing server controlsClean HTML makes CSS and JavaScript easierWhat 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 projectVery easy to setup if you follow these rulesNeeds to be in a “form” tag, not Html.BeginForm()Handlers need to be changed from .aspx to .axdDialogHandlerUrl, SpellCheckChettingsUse a custom tools fileASP.NET MVCTelerikRadEditor

Setting<% RadEditor1.Content = Model.Description %>GettingNeed to pass in the request and name of editorASP.NET MVCTelerikRadEditor Set and Get Contentvarcontent = _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 2008Not widely thought of by the communitySecond version (V4) is set to be released with .NET 4Maps POCO objects to Database objectsA collection of things instead of a dataset of rows“things” are the EntitiesEntity Framework

Why?Adds a layer of abstraction between Database and CodeDBA can structure DB how they wantDeveloper can map to the DB how they wantRename Entities for more comfortable use.EF handles the mappingEntity Framework

Entity Data Model – EDMDeals with the Entities and the Relationships they useEntitiesInstance of EntityTypeRepresent individual instances of the objectsCustomer, books, shoesFully typedRelationshipsV1 was difficult to work with relationshipsNeeded special tricks to load related dataEntity FrameworkDefinitions

Adding an EDM to your projectDemo

A design pattern to defer initialization until needed.EF 4 fixes a lot of problems with thisSupports Lazy LoadingOFF by defaultObjectContext setting, not application settingcontext.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 entityList<Thing> things = context.Things.Include(“ThingItems”);foreach(var thing in things){varthingItems = thing.ThingItems}Entity FrameworkEager Loading

The context is the instance of the entityPassing an entity around to tiers breaks the contextV4 will handle this issue with “self-tracking” entitiesMake sure the context is always the sameEntity FrameworkContexts

Entity FrameworkContextspublic 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();

Entity FrameworkContextsprivate Student AddStudent(Student student, Course course){student.Courses.Add(course);_db.SaveChanges();}Didn’t work because course was in a different contextprivate 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 SQLMajor differenceLINQ 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 createdEntity FrameworkLINQ to Entities

James Johnsonjames@iedotnetug.orgwww.duringlunch.comTwitter, @latringoInland Empire .NET User’s Groupwww.iedotnetug.org2nd Tuesday’s of each month in RiversideThank you

MVC and Entity Framework 4

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