MVC and Entity Framework

ASP.NET MVC and Entity FrameworkUtah Code CampSaturday, September 25, 2010James JohnsonTechnical Evangelist

Technical Evangelist with ComponentOneFounder and President of the Inland Empire .NET User’s GroupMicrosoft 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 new coins during the presentationWho am I?

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

ModelsViewsControllersNo PostbacksVery limited use of existing server controlsClean HTML makes CSS and JavaScript easierWhat all the cool kids are using these days.ASP.NET MVC

First version (V 1) came with .NET 3.5 SP1 August 2008Not widely thought of by the communitySecond version (V4) 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 this

ObjectContext 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 handles 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

MVC and Entity Framework

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MVC and Entity Framework