Lesson 1 ADO.NET

 ADO.NET is a set of classes that allows .NET Framework programmers to interact with data sources The data source is a database such as Microsoft SQL Server, Microsoft Access, Oracle,.

 ADO.NET is a set of classes that allows NET Framework programmers to interact with data sources

 The data source is a database (such as Microsoft SQL Server, Microsoft Access, Oracle, ), but it could also be a text file,

an Excel spreadsheet, or an XML file

 The System.Data namespace contains the core data access classes in the NET Framework

 The design goals of ADO.NET:

 Leverage current ActiveX Data Objects (ADO) knowledge

 Support the n-tier programming model

 Integrate XML support

Introduction to ADO.NET

 The two main components of ADO.NET for accessing and manipulating data:

 The NET Framework Data Providers

 There isn't a single set of classes that allow you to interact with different types of data sources and different types of databases

 A way to communicate with the right data source using the

ADO.NET Components (cont.)

ADO.NET architecture

Data Provider Description Namespace

 Core objects of NET Framework Data Providers

ADO.NET Components

The NET Framework Data Providers (cont.)

Object Description

Connection Establishes a connection to a specific data source The

connection helps identify the database server, the database name, user name, password, and other parameters

Command Executes a command against a data source: get data,

modify data, run stored procedures, and send or retrieve parameter information

DataReader Reads a forward-only, read-only stream of data from a data

source

DataAdapter Populates a DataSet and resolves updates with the data

source: the bridge between the DataSet object and the data source

 Each data provider provides an implementation of the

Connection, Command, DataAdapter, and

DataReader objects

ADO.NET Components

The NET Framework Data Providers (cont.)

Slide 9

 Connected data access through the DataReader objects of

data provider This object provides forward-only, read-only access to data in the data source

 Disconnected data access is achieved through the

DataAdapter object This object loads data in the DataSet that works independent of database and can edit the data

Connected and disconnected data access

DataReader

DataSet DataAdapter

Connected

 What is a Connection object?

 Creating and configuring Connection objects

 Working with Connection pools

 Handling Connection errors

 Enumerating the available SQL Servers

 Securing sensitive Connection string data

Connection objects

Slide 11

What is a Connection object?

 A Connection object is a representation of an connection

to a specific data source

 The Connection helps identify the database server, the database name, user name, password, and other

parameters

How to create Connection?

 Creating Connections in Server Explorer

Read only Get the name of the current database after a connection is opened or the database name specified in the connection string before the connection is opened

DataSource Read only Get the name of the database server to which it is connected.

State Read only Get a string that describes the state of the connection.

Connection methods

Name Description

Open Open a database connection with the settings

specified by the ConnectionString You cannot open

the connection that is opened

Close Close the connection to the database This is the

preferred method of closing any open connection.

15

Open connection

 Open the connection with database Northwind:

SqlConnection conn = new SqlConnection();

conn.ConnectionString = " Data Source=localhost; Initial

Catalog=Northwind; Integrated Security=SSPI";

conn.Open();

 Open the connection with database QLSV.accdb:

OleDbConnection conn = new OleDbConnection();

conn.ConnectionString = "Provider=Microsoft.ACE.OLEDB.12.0;

Data Source = QLSV.accdb";

conn.Open();

Connection String

Parameter Name Description

Data Source Identifies the server Could be local machine, machine domain name, or IP

Address.

Initial Catalog Database name.

Integrated

Security Set to SSPI to make connection with user's Windows login

User ID Name of user configured in SQL Server Password Password matching SQL Server User ID.

Slide 17

What is connection pooling? (p 225)

 Connection pooling enables the reuse of existing

connections

 This technique allows storage of connection has been

established in Connetion Pool in a time period, and

applications needed to access the database may require a connection from this Connection Pool

 That improves performance, increase the scalability of an application

 Connections have the same configuration

 Each time call Open method with a unique connection

string, a new pool is created

Controlling Connection pooling options

 By default, connection pooling is enabled when creating

ADO.NET connection (Pooling = True)

 Control connection pooling behavior by setting connection string

 Pooling

 Min Pool Size

 Max Pool Size

19

Configuring Connections to Use

Connection Pooling

 Configuring Connection Pooling with SQL Server

Connections

 Data Source=SqlServerName;Initial Catalog=DatabaseName;

Integrated Security=True;Min Pool Size=5

 Configuring Connection Pooling with OLE DB Connections

 Provider=Microsoft.Jet.OLEDB.4.0;Data

Source=DatabaseName.mdb;OLE DB Services=-1

 (See page 228-229)

Handling Connection Errors

 .NET Exceptions

21

Handling Connection Errors

 OleDbException class exposes properties that contain

details of the exception condition These include:

 A Message property that contains text describing the error.

 A Number property that contains the error number, which

uniquely identifies the type of error.

 A State property that contains additional information about

the invocation state of the error.

 An Errors collection, which contains detailed error

information about the errors.

Handling Connection Errors

try {

conn.Open();

// using conn }

catch ( OleDbException ex)

Enumerating the Available SQL (p.237)

 Using Instance property of the SqlDataSourceEnumerator class to call the GetDataSources method

 The GetDataSources method returns a Data-Table that contains information for each SQL server that is visible on the network

System.Data.Sql.SqlDataSourceEnumerator instance =

System.Data.Sql.SqlDataSourceEnumerator.Instance;

dataGridView1.DataSource = instance.GetDataSources();

Enumerating the Available SQL

 Why no SQL Servers appear?

 Network traffic

 Firewall

 Service SQL Browser need to run

25

Securing Sensitive Connection String Data (p 241)

 Protect your application

 Secure information such as user IDs, data source names, passwords,…

 The suggested method of implementing security in

applications

 Windows Authentication (Integrated Security)

27

Securing Sensitive Connection String Data (p 241)

 The suggested method of implementing security in

applications (cont.)

 Using the application configuration file (app.config)

 Add\Add new item, select 'Application Configuration file'

Securing Sensitive Connection String Data (p 241)

 The suggested method of implementing security in

applications (cont.)

 Encrypt config file: available in the NET Framework (Lab: p 243)

29

 Creating and configuring Command objects

 Executing Command objects

 Working with parameters in SQL commands

Command objects

 Command object is a object which is used to

 Execute SQL statements ( INSERT, DELETE, UPDATE or SELECT

statement)

 Execute Stored procedures

 Create Command object:

 XxxCommand cmd = new XxxCommand ();

 XxxCommand cmd = new XxxCommand (string

commandText);

 XxxCommand cmd = new XxxCommand (string

commandText, XxxConnection connection);

Slide 31

Creating Command objects

Example database

Slide 33

 Example 1: Querying data

OleDbCommand cmd = new OleDbCommand ();

cmd.Connection = conn;

cmd.CommandType = CommandType.Text ;

cmd.CommandText = "select * from SinhVien ";

 Example 2: Querying data

OleDbCommand cmd = new OleDbCommand ();

cmd.Connection = conn;

cmd.CommandType = CommandType.TableDirect ;

cmd.CommandText = "SinhVien ";

Example 1, 2

 Example 3: Inserting data

OleDbCommand cmd = new OleDbCommand ();

cmd.Connection = conn;

cmd.CommandType = CommandType.Text;

"VALUES ('CSE', 'Khoa Khoa Học và Kỹ Thuật Máy Tính') " ;

 Example 4: Deleting data

OleDbCommand cmd = new OleDbCommand ();

 Example 5: Updating data

OleDbCommand cmd = new OleDbCommand ();

cmd.Connection = conn;

cmd.CommandType = CommandType.Text;

SET GVCN = 'Tran Thi B'

WHERE MaLop = 'CDTH10K'";

 Example 6: Getting single values

OleDbCommand cmd = new OleDbCommand ();

cmd.Connection = conn;

cmd.CommandType = CommandType.Text;

Example 5, 6

 Example 7: Querying data using stored procedure

OleDbCommand cmd = new OleDbCommand();

 To execute a Command object, using methods:

 ExecuteScalar(): returns an object

 Executes SQL statements or Stored procedures that return a single value (SELECT statement)

 ExecuteNonQuery(): returns an integer

 Executes SQL statements or Stored procedures and returns the number of rows that were affected but do not return data

(INSERT, DELETE, UPDATE, CREATE TABLE statement)

 ExecuteReader(): returns a DataReader object

 Executes SQL statements or Stored procedures that returns the DataReader object (SELECT statement)

Executing Command objects

 How to create a query with undefined value?

 Concatenate string in query

 What is Parameterized query?

 Types of Parameter

 How to pass value to Parameter query?

Working with Parameters in SQL

commands

 Parameterized queries are queries that have one or more embedded parameters in the SQL statement

 SQL Server uses the @ symbol as a prefix to denote named parameters

 Other databases (such as Microsoft Office Access and OLE DB data sources) represent parameters with a question mark (?) symbol

What is Parameterized query?

 Types of Parameter:

 Input parameter (default)

 send data to the database

 Output parameter

 retrieve information coming out of the database

 InputOutput parameter

 The type of parameter is designated in the Direction

property of the parameter

 With a parameter, you can set its Direction property to Input ,

Output , InputOutput , or ReturnValue

Types of Parameter (p.274)

1. Declare an instance of the Parameter class with its name

and data type

2. Set Value for parameter

3. Choose ParameterDirection (if needed)

4. Add parameter to the Parameters collection of the