Intro to C# .net and EF

Ilan Shimshoni

The Three Faces of ADO.NET

• The connected layer– Directly connecting to the DB

• The disconnected layer– Using datasets

• Connection through the Entity Framework (EF)– Automatically defining the relation between the

DB and the C# classes and working with LINQ.

The connected layer

.Net Platform Data Provider

Database

ClientAssembly

Connection Object

Connection Object

DataReader Object

DataAdaptor Object

Transaction

Parameter Collection

Select Command

Update Command

Delete Command

Insert Command

Insert Method public void InsertAuto(NewCar car) { // Format and execute SQL statement. string sql = string.Format("Insert Into Inventory" + "(CarID, Make, Color, PetName) Values" + "('{0}', '{1}', '{2}', '{3}')", car.CarID, car.Make, car.Color, car.PetName);

// Execute using our connection. using (SqlCommand cmd = new SqlCommand(sql, this.sqlCn)) { cmd.ExecuteNonQuery(); } }

Select Method public List<NewCar> GetAllInventoryAsList() { // This will hold the records. List<NewCar> inv = new List<NewCar>();

// Prep command object. string sql = "Select * From Inventory"; using (SqlCommand cmd = new SqlCommand(sql, this.sqlCn)) { SqlDataReader dr = cmd.ExecuteReader(); while (dr.Read()) { inv.Add(new NewCar { CarID = (int)dr["CarID"], Color = (string)dr["Color"], Make = (string)dr["Make"], PetName = (string)dr["PetName"] }); } dr.Close(); } return inv; }

DataSets

Client Application

DataSet Data Adapter Database

DataSets

• Represents a database in memory• Includes:– Tables– Relationships– Tables in include columns (fields)

• Constraints• Name• Datatype• Unique?• Column number (ordinal)

DataSets

• When the dataset is modified• The modifications are known• Errors are detected• They can be written back to the database

using the DataAdapter• They can be rolled back

Datasets Gui and LinQ private void CreateDataView2() { dataGridYugosView.DataSource = from car in inventoryTable where (string)car["Make"] == "Yugo" select car;

dataGridYugosView.DataError += new DataGridViewDataErrorEventHandler(DataGridView1_DataError); }

The Entity Framework

The third layer

EF

• Separate the strong link between the DB and the program

• Build strongly typed objects classes to represent the DB in the program. These objects are called the Entity Data Model(EDM)

• A set of XML files called edmx files connect between the DB and the EDM classes.

EF components

• Object Services: – all EDM classes inherit from EntityObject. Its in charge

of monitoring modifications to the object in order to then update the corresponding DB record(s)

• EntityClient namespace:– Its like a data provider but fro EDM objects.

• *.edmx files:– Conceptual model (Describe EDM classes)– Physical model (Describe DB tables and rels)– Logical model (relates the EDM to the DB tables)

All Together Now

C# Code

Object Services

Entity Client Data Provider

ADO.NET Data Provider

Physical Database

DbDataReader

EntityDataReader

*.edmx

IEnumerable<T>LINQ QueryEntity SQLEntity SQL

Command Tree

Command Tree

*.edmx files: DB Storage<edmx:StorageModels> <Schema Namespace="AutoLotModel.Store" Alias="Self" Provider="System.Data.SqlClient" ProviderManifestToken="2005" xmlns:store="http://schemas.microsoft.com/ado/2007/12/edm/EntityStoreSchemaGenerator" xmlns="http://schemas.microsoft.com/ado/2009/02/edm/ssdl"> <EntityContainer Name="AutoLotModelStoreContainer"><EntitySet Name="Inventory" EntityType="AutoLotModel.Store.Inventory" store:Type="Tables" Schema="dbo" /><EntityType Name="Inventory"> <Key> <PropertyRef Name="CarID" /> </Key> <Property Name="CarID" Type="int" Nullable="false" /> <Property Name="Make" Type="varchar" Nullable="false" MaxLength="50" /> <Property Name="Color" Type="varchar" Nullable="false" MaxLength="50" /> <Property Name="PetName" Type="varchar" MaxLength="50" /> </EntityType></Schema></edmx:StorageModels>

Conceptual Model (EDM)<edmx:ConceptualModels> <Schema Namespace="AutoLotModel" Alias="Self" xmlns:annotation="http://schemas.microsoft.com/ado/2009/02/edm/annotation" xmlns="http://schemas.microsoft.com/ado/2008/09/edm"> <EntityContainer Name="AutoLotEntities" annotation:LazyLoadingEnabled="true"><EntitySet Name=“Cars" EntityType="AutoLotModel.Car" /> <EntityType Name="Inventory"> <Key> <PropertyRef Name="CarID" /> </Key> <Property Name="CarID" Type="Int32" Nullable="false" /> <Property Name="Make" Type="String" Nullable="false" MaxLength="50" Unicode="false" FixedLength="false" /> <Property Name="Color" Type="String" Nullable="false" MaxLength="50" Unicode="false" FixedLength="false" /> <Property Name=“CarNickname" Type="String" MaxLength="50" Unicode="false" FixedLength="false" /></Schema> </edmx:ConceptualModels>

C-S mapping<edmx:Mappings> <Mapping Space="C-S" xmlns="http://schemas.microsoft.com/ado/2008/09/mapping/cs"> <EntityContainerMapping StorageEntityContainer="AutoLotModelStoreContainer" CdmEntityContainer="AutoLotEntities"> <EntitySetMapping Name=“Cars"><EntityTypeMapping TypeName="AutoLotModel.Car"><MappingFragment StoreEntitySet="Inventory"> <ScalarProperty Name="CarID" ColumnName="CarID" /> <ScalarProperty Name="Make" ColumnName="Make" /> <ScalarProperty Name="Color" ColumnName="Color" /> <ScalarProperty Name=“CarNickname" ColumnName="PetName" /> </MappingFragment></EntityTypeMapping> </EntitySetMapping></Mapping> </edmx:Mappings>