Entity Framework - Simplified by Mohd Manzoor Ahmed - HTML preview

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Introduction To Entity Framework:

 The Microsoft ADO.NET Entity Framework is an Object/Relational Mapping (ORM)

framework that enables developers to work with relational data as domain-specific

objects, eliminating the need for most of the data access plumbing code that

developers usually need to write.

 Using the Entity Framework, developers issue queries using LINQ, then retrieve and

manipulate data as strongly typed objects. The Entity Framework’s ORM

implementation provides services like change tracking, identity resolution, lazy

loading, and query translation so that developers can focus on their application-

specific business logic rather than the data access fundamentals.

- Definition of Entity Framework given by Microsoft

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Entity Framework - Simplified

Various approaches to work with Entity Framework:

 Database First (This eBook is Focused on):

o Creating the model from database (Generating Classes or Class Diagram

from Database Tables).

 Model First

o Creating the database from model (Generating Database Tables from Classes

or Class Diagram).

 Code First (Some Time POCO)

o Coding classes against the existing Database is Code First.

o Creating the database from the coded classes(No class diagrams) is POCO.

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Entity Framework - Simplified

Chapter 2: Creating an Entity Data Model

 In this chapter, I’m going to show you How to create your Entity Data Model.

 This is very simple. I’ve a database called as organization in which I’ve department

table and employee table.

 I’m going to use the same database throughout our course on Entity Framework.

 So, In Department table I’ve Did(Department ID), Dname(Department Name), HOD

and Gender in which Did is primary key.

 In Employee table I’ve Eid(Employee ID), Ename(Employee Name), Esal(Employee

Salary), EGen(Employee Gender), EDOB(Employee Date Of Birth) and Did is the

foreign key from department table.

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Entity Framework - Simplified

Creating Entity Data Model:

 Create a web Project say EntityFrameworkPart-1

 Lets create our entity data model(EDM) which is the heart of Entity Framework and it

is very simple.

 I’ll goto my Project what I’ve created as EntityFrameworkPart-1

 Right click the project

 Add new item

 Select ADO.NET Entity Data Model

 And I’ll name it as OrganizationModel.edmx

 Click Add

 It is going to add in App_Code folder

 I’ll say yes

 It’ll fire a window with two options for me.

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Entity Framework - Simplified

1. Generate Empty Database (Create a model from an existing database)

2. Empty Model (Create model first then create the database)

 As I want to generate Entity Data Model from an existing database. Select Generate

Empty Database click Next.

 You’ll see the database is organization and Entity connection string (same as your

connection string which provides the information about the provider, DataSource,

Initial Catalog , UserID, Password, Integrated Security….)

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Entity Framework - Simplified

 The connection string also contains some extra information as metadata about your

Entity Framework. Save entity connection settings in Web.Config as

OrganizationEntities click next.

 At this point It’ll retrieve the database information (tables, stored procedures..) As

of now I’m going to work with two tables “tbl_Dept” and “tbl_Emp”. I’m going to add

these two tables to my Entity Data Model

 Leave the options checked for Pluralize or Singularize generated object names and

Include foreign key columns in the model click on Finish.

 Here’s my Entity Data Model

 As you might have seen, in a single department I can have n number of employees.

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Entity Framework - Simplified

 So, we’ve one-to-many relationship and all the columns that I’ve in the database

are turned into properties for both the tables.

 There are two extra properties called as Navigation Properties. That means whenever

I’ve relation between two tables for navigation from either tbl_Dept to tbl_Emp or

tbl_Emp to tbl_Dept .

 So, this is my Entity Data Model.

 Right click on Entity Data Model

 Open with XML Editor Click Ok then Yes for Prompt window

 This is the XML file that is generated automatical y for Entity Data Model

 Let us have a look into this XML file and let us see what it contains

1. Runtime tag <edmx:Runtime> and

2. Designer tag <Designer>

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Entity Framework - Simplified

 The Designer tag contains some UI related to our Entity Data Model (Graphical table

data)

 The Runtime tag consists of 3 parts

1. SSDL (Storage Schema Definition Language) [Info about database, tables,

columns.. for SQL data]

<edmx:StorageModels>

<Schema Namespace="OrganizationModel.Store " Alias="Self" Provider="System.Data.SqlClient "

ProviderManifestToken="2008"

xmlns:store="http://schemas.microsoft.com/ado/2007/12/edm/EntityStoreSchemaGenerator"

xmlns="http://schemas.microsoft.com/ado/2009/02/edm/ssdl">

<EntitySet Name="tbl_Dept" EntityType="OrganizationModel.Store.tbl_Dept"

store:Type="Tables" Schema="dbo" />

<EntitySet Name="tbl_Emp" EntityType="OrganizationModel.Store.tbl_Emp" store:Type="Tables"

Schema="dbo" />

<AssociationSet Name="FK_tbl_Emp_tbl_Dept "

Association="OrganizationModel.Store.FK_tbl_Emp_tbl_Dept">

</AssociationSet>

</EntityContainer>

<Key>

</Key>

</EntityType>

<Key>

</Key>

</EntityType>

</Principal>

</Dependent>

</ReferentialConstraint >

</Association>

<Function Name="SP_GetAllEmployee" Aggregate="false" BuiltIn="false"

NiladicFunction="false" IsComposable="false"

ParameterTypeSemantics="AllowImplicitConversion" Schema="dbo" />

<Function Name="SP_GetEmployeesByDid" Aggregate="false" BuiltIn="false" NiladicFunction="false"

IsComposable="false" ParameterTypeSemantics="AllowImplicitConversion" Schema="dbo">

</Function>

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Entity Framework - Simplified

<Function Name="SP_GetEmpNameAndSalaryByEid" Aggregate="false" BuiltIn="false"

NiladicFunction="false" IsComposable="false"

ParameterTypeSemantics="AllowImplicitConversion" Schema="dbo">

</Function>

</Schema></edmx:StorageModels>

2. CSDL (Conceptual Schema Definition Language) [Properties for each table and each

column.. for C# data]

<edmx:ConceptualModels >

<Schema Namespace="OrganizationModel" Alias="Self"

xmlns:annotation="http://schemas.microsoft.com/ado/2009/02/edm/annotation"

xmlns="http://schemas.microsoft.com/ado/2008/09/edm">

<AssociationSet Name="FK_tbl_Emp_tbl_Dept"

Association="OrganizationModel.FK_tbl_Emp_tbl_Dept">

</AssociationSet>

<FunctionImport Name="SP_GetAllEmployee"

ReturnType="Collection(OrganizationModel.SP_GetAl Employee_Result)" />

<FunctionImport Name="SP_GetEmployeesByDid"

ReturnType="Collection(OrganizationModel.SP_GetEmployeesByDid_Result)">

</FunctionImport >

</FunctionImport >

</EntityContainer>

<Key>

</Key>

<Property Name="Did" Type="Int32" Nul able="false"

annotation:StoreGeneratedPattern="Identity" />

<Property Name="HOD" Type="String" Nul able="false" MaxLength="50" Unicode="false"

FixedLength="false" />

<Property Name="Gender" Type="String" Nul able="false" MaxLength="50" Unicode="false"

FixedLength="false" />

<NavigationProperty Name="tbl_Emp" Relationship="OrganizationModel.FK_tbl_Emp_tbl_Dept"

FromRole="tbl_Dept" ToRole="tbl_Emp" />

</EntityType>

<Key>

</Key>

<Property Name="Eid" Type="Int32" Nul able="false"

annotation:StoreGeneratedPattern="Identity" />

<Property Name="EName" Type="String" Nul able="false" MaxLength="50" Unicode="false"

FixedLength="false" />

<Property Name="EGen" Type="String" Nul able="false" MaxLength="10" Unicode="false"

FixedLength="false" />

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Entity Framework - Simplified

<NavigationProperty Name="tbl_Dept"

Relationship="OrganizationModel.FK_tbl_Emp_tbl_Dept " FromRole="tbl_Emp" ToRole="tbl_Dept "

</EntityType>

</Principal>

</Dependent>

</ReferentialConstraint >

</Association>

</ComplexType>

</ComplexType>

</Schema>

</edmx:ConceptualModels >

3. C-S Mapping [Column Mappings]

<edmx:Mappings>

<EntityContainerMapping StorageEntityContainer="OrganizationModelStoreContainer"

CdmEntityContainer="OrganizationEntities">

<EntitySetMapping Name="tbl_Dept "><EntityTypeMapping

TypeName="OrganizationModel.tbl_Dept"><MappingFragment StoreEntitySet="tbl_Dept">

</MappingFragment ></EntityTypeMapping></EntitySetMapping>

<EntitySetMapping Name="tbl_Emp"><EntityTypeMapping

TypeName="OrganizationModel.tbl_Emp"><MappingFragment StoreEntitySet="tbl_Emp">

</MappingFragment ></EntityTypeMapping></EntitySetMapping>

<FunctionImportMapping FunctionImportName="SP_GetAllEmployee"

FunctionName="OrganizationModel.Store.SP_GetAl Employee ">

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Entity Framework - Simplified

</ComplexTypeMapping>

</ResultMapping>

</FunctionImportMapping>

<FunctionImportMapping FunctionImportName="SP_GetEmployeesByDid"

FunctionName="OrganizationModel.Store.SP_GetEmployeesByDid ">

</ComplexTypeMapping>

</ResultMapping>

</FunctionImportMapping>

<FunctionImportMapping FunctionImportName="SP_GetEmpNameAndSalaryByEid"

FunctionName="OrganizationModel.Store.SP_GetEmpNameAndSalaryByEid " />

</EntityContainerMapping>

</Mapping>

</edmx:Mappings>

 CLR generates 3 different files for Runtime tag at runtime.

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Entity Framework - Simplified