Entity Framework - Entity Data Model (edm)

Entity Data Model (EDM)

Eyal Vardi
CEO E4D Solutions LTD
Microsoft MVP Visual C#
blog: www.eVardi.com

EF Architecture

LINQ to Entities Entity SQL EDM
Conceptual
Object Services Model

Mapping
Entity Client Provider
Storage
ADO.NET Provider Model

SQLServer

© 2010 E4D LTD. All rights reserved. Tel: 054-5-767-300, Email: Eyal@E4D.co.il

 The EDM is the link between the model and
the database.
 The EDM is that it decouples your application
from the underlying store.

Conceptual Storage
Mapping
Model Model Storage
(MSL)
(CSDL) (SSDL)


Agenda
LINQ to Entity EDM
Entities SQL

Conceptu
Object Services al Model

Mapping

Storage
Model
ADO.NET Provider

 EF Architecture

 Development Approaches

 Entity Data Model (EDM)

 Object Services

 Querying & Loading Entities


LINQ to Entity EDM
Entities SQL

Conceptu

Mapping

Storage
Model
ADO.NET Provider

Development Approaches


Database First
 If you already have a database, the Entity
Framework can automatically generate a data
model that consists of classes and properties
that correspond to existing database objects
such as tables and columns.

Generated
Database First Data Model
DB
(.edmx)


Model First
 If you don't yet have a database, you can
begin by creating a model using the Entity
Framework designer in Visual Studio.
 The designer can generate DDL (data definition language)
statements to create the database.

Data Model Model First Generated
(.edmx)
DB


Code First
 Whether you have an existing database or not, you
can code your own classes and properties that
correspond to tables and columns and use them with
the Entity Framework without an .edmx file.

Data Model Code First Generated
(Classes)
DB

Generated
Code First Data Model
DB
(Classes)


Conventions
 The pluralized forms of entity class names are
used as table names.

 Entity property names are used for column
names.

 Entity properties that are named ID or
classnameID are recognized as primary key
properties.


LINQ to Entity EDM
Entities SQL

Conceptu

Mapping

Storage
Model
ADO.NET Provider

Database Configuration


Database Configuration(Code First)

DB Name Connection Name
(no config file )


Initialization Strategy (Code First)
 Initialize the database, the first time a context
is used in an AppDomain.
 The following initializers are supported:
 CreateDatabaseIfNotExist
 DropCreateDatabaseAlways
 DropCreateDatabaseIfModelChanges


Seeding a Database (Code First)
 The Seed method takes whatever you put in
the context and saves it to the database.
 you don’t need to call SaveChanges but you DO need to be
sure to call the base Seed method at the end.
 Database.SetInitializer( new DbInit() );


Database Configuration
 Model First is different from Code First in that
your Entity Data Model (EDM) already exists.


LINQ to Entity EDM
Entities SQL

Conceptu

Mapping

Storage
Model
ADO.NET Provider

Data Annotations


Data Annotations
 Code first gives you two ways to add these
configurations to your classes.
 Data Annotations

 Fluent API


Data Annotations
 Map your code first classes to a pre-existing
database.
 Key  DatabaseGenerated
 NotMapped  InverseProperty
 ComplexType  ForeignKey
 ConcurrencyCheck
 TimeStamp
 Table and Column

MSDN link

Validation Attribures
 Validation your code first classes.
 Required
 StringLength
 MaxLength & MinLength

public class ProductMD
{
[StringLength(50)]
[Required]
public object Name { get; set; }

[Required]
public object Weight { get; set; }
}


Validations
 DbContext automatically validates entities
before saving them to the database.
 Validation is performed based on model facets
as well as on data annotations. Entities can
also be validated on demand.


Data Annotations


LINQ to Entity EDM
Entities SQL

Conceptu

Mapping

Storage
Model
ADO.NET Provider

Fluent API


Fluent API
 Specify additional mapping configuration that
will override the default Code First
conventions.
 Map to an existing database schema or to
affect the shape of a generated schema.


Fluent API (DbModelBuilder)
 Fluent API Exposed through the
DbModelBuilder.
 Properties with Fluent API

 Types with Fluent API

 Relationships with Fluent API


Fluent API (Types)
 Specifying
 Complex Type

 Not to map a CLR entity type to a table in the database

 Mapping
 a CLR entity type to a specific table in the database

 The table-per-hierarchy (TPH) inheritance

 The table-per-type (TPT) inheritance

 The table-per-concrete class (TPC) inheritance

 CLR properties of an entity type to multiple tables in the database

 Multiple entity types to one table in the database


Fluent API (Types)

Fluent API Samples (Click)

Fluent API (Relationships)
 Configuring:
 a one-to-zero-or-one relationship
 a relationship where both ends are required
 a many-to-many relationship
 a relationship with one navigation property
 a composite foreign key
 a foreign key name that does not follow the Code First
convention

 Enabling cascade delete

 Renaming a foreign key that is not defined in the
model

Relationships (HasXXXWithXXX)
Principal Dependent

modelBuilder.Entity<Course>()
.HasRequired( t => t.Department)
.WithMany( t => t.Courses)
.HasForeignKey(d => d.DepartmentID)
.WillCascadeOnDelete(false);


Fluent API (Relationships)


Cascade Delete
 You can configure cascade delete on a
relationship by using the
WillCascadeOnDelete method.
 You can remove these cascade delete
conventions by using:
 modelBuilder.Conventions.Remove<OneToManyCascadeDeleteConvention>()
 modelBuilder.Conventions.Remove<ManyToManyCascadeDeleteConvention>()

modelBuilder.Entity<Course>()
.HasRequired( t => t.Department)
.WithMany( t => t.Courses)
.HasForeignKey(d => d.DepartmentID)
.WillCascadeOnDelete(false);


Fluent API (Properties)
 Primary & Foreign key

 Maximum length

 Required

 Mapping a CLR property to a specific column in the database

 Unicode content

 Data type of a database column

 Complex type

 Optimistic concurrency token


Fluent API
(Properties)


LINQ to Entity EDM
Entities SQL

Conceptu

Mapping

Storage
Model
ADO.NET Provider

Inheritance Mapping


Inheritance Mapping
 Inheritance mapping strategies:
 Table per Hierarchy (TPH)

 Table per Type (TPT)

 Table per Concrete Type (TPC)


Table per Hierarchy (TPH)
 An entire class hierarchy can be mapped
to a single table.
 This table includes columns for all properties of
all classes in the hierarchy.


TPH with Fluent API
 The code will change the discriminator column name
to "BillingDetailType" and the values to "BA" and
"CC" for BankAccount and CreditCard respectively:

Click here for more information

Table per Type (TPT)
 TPT is about representing inheritance relationships as
relational foreign key associations.
 Every class/subclass that declares persistent properties—
including abstract classes—has its own table.


TPT with Fluent API
 TPT mapping by using ToTable() method.


Table per Concrete Type (TPC)
 In TPC type we use exactly one table for each
(nonabstract) class.


Fluent API


Entity Framework - Entity Data Model (edm)

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