The Entity Data Model by LearnNowOnline

The Entity Data Model

Learn More @ http://www.learnnowonline.com Copyright ÂŠ by Application Developers Training Company

Objectives • Learn how to create and use an Entity Data Model • Explore the raw XML behind the model as a way to understand how Entity Framework works • See how to use stored procedures within an Entity Framework model

Agenda • • • •

Introduction Creating and Using an Entity Data Model Entity Data Model in the Raw Using Stored Procedures in the Model

Introduction • Key link between entity objects and data  Conceptual model  Storage model  Mapping model

• Application design is often at odds with database design • Can work with model in designer  Or get messy with the XML

The Models within the Model • Conceptual Model  The actual Entity Data Model  Provides what is needed to create data objects

• Storage Model  Represents the database schemas  Can be similar to conceptual model  Decupling of conceptual design from the database

• Mapping Model  Bridge between conceptual and storage models  Map object properties to database fields Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company

Agenda • • • •

Introduction Creating and Using an Entity Data Model Entity Data Model in the Raw Using Stored Procedures in the Model

Creating and Using an Entity Data Model • Can create from scratch using XML  More productive using the designer

• Three approaches  Database-first  Model-first  Code-first

Creating a Model Using DatabaseFirst Design • Directly supported by the Entity Framework template • Wizard lets you  Reverse-engineer the database schma  Select tables, views, and stored procedures to include  Build the model from selected objects

Multiplicity • Used with associations • Number of entities that can be on each end of an association  Sometimes referred to as cardinality

• Three options  One: 1  Zero or one: 0..1  Many: *

Entity Data Model Object Properties • Typical for Visual Studio • Use Properties windows to set values of properties for various objects • Model stores some in model’s XML to define a model, others guide object creation

Creating a Model Using Model-First Design • Database-first design is common • Sometimes creating a new database with the application  Could create the database first  But model-first is another option  Strictly speaking, Entity Framework has always had this option

Sled Dog Event Registration Event Name EventDate Sponsor Location

Race Distance DogCount Trail

Mushing Leader1 Leader2

Team FirstName LastName City Country DogCount

Skijoring Dog1 Dog2 Dog3 NumberOfLeaders

Learn More @ http://www.learnnowonline.com Copyright ÂŠ by Application Developers Training Company

Explore the Model with the Model Browser • Working with large models can be hard in the designer  Can be hard to understand the structure of the model  Mapping Details windows doesn’t have details of storage model

• Overcome these limitations with the Model Browser

Agenda • • • •

Introduction Creating and Using an Entity Data Model Entity Data Model in the Raw Using Stored Procedures in the Model

Entity Data Model in the Raw • Designer is a graphical view only of the conceptual model  Exposes most, but not all, features  Ultimately, just a pretty face on the XML

• Need to have a basic understanding of the XML  Sometimes have to manipulate the XML directly

• Can use any text editor  But Visual Studio XML editor provides color-coding, wellformedness checks, and Intellisense

XML Definition Languages • One for each model:  Conceptual model uses Conceptual Schema Definition Language (CSDL)  Storage model uses Store Schema Definition Language (SSDL)  Mapping model uses Mapping Specification Language (MSL)

• Visual Studio includes XML schema files

Model Build Mechanics • .edmx file contains XML for all three models  Plus support for the graphical designer

• Saves as three files at build:  Conceptual model to .csdl file  Storage model to .ssdl file  Mapping model to .msl file

• By default, stored in project assembly  Can output three physical files  Change the MetadataArtifactProcessing property of the entity container Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company

Agenda • • • •

Introduction Creating and Using an Entity Data Model Entity Data Model in the Raw Using Stored Procedures in the Model

Using Stored Procedures in the Model • Entity Framework can automatically generate all code needed to do CRUD • Not necessarily ideal from DBA’s perspective  Job is to make sure data is secure, performs well, is scalable, and meets needs of the application  Dynamic SQL complicates the job

• Stored procedures vs. dynamic code  Pick one or the other and go for it

Ways to Use Stored Procedures • Few different ways  Replace an entity’s insert, update, and delete functions to use stored procedures  Use stored procedures that return data to entities are scalar values

• Entity Framework uses terms stored procedure and function interchangeably

Updating the Model from the Database • Have to include stored procedures in the model before you can use them  Only imported tables and views

• Entity Framework supports updating the model from the database • Will use several stored procedures    

InsertCustomer, UpdateCustomer, and DeleteCustomer GetCustomersByRegion GetProductListByCategory GetProductCategoryAveragePrice Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company

Using Stored Procedures to Change an Entity • One of the most common ways to use stored procedures • Replaces Entity Framework default behavior for an entity • Will use the Customer object

Using Stored Procedures that Read Data • Use stored procedures that read data in the model  Materialize an entity object  Random sets of data

• GetCustomersByRegion returns all of the fields of the Customer table • GetProductListByCategory returns fields from the Product and ProductCategory tables • Complex type  Neither an entity or scalar type  Use Model Browser to work with Learn More @ http://www.learnnowonline.com Copyright © by Application Developers Training Company

Using Stored Procedures that Return a Scalar Value • Another option is to retrieve a scalar value from a stored procedure • Dirty little secret  Stored procedure still returns a result set  Entity Framework extracts the value, sort of

Learn More! • This is an excerpt from a larger course. Visit www.learnnowonline.com for the full details! • Learn more about Entity Framework on SlideShare:  Introducing the Entity Framework