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Getting Started With ADO.NET

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ADO.NET ADO was a good architecture but as the language changes so is the

technology. ADO was a connected data access, which means that

when a connection to the database is established the connection

remains open until the application is closed.

ADO.NET is a data-access technology that enables applications to

connect to data stores and manipulate data contained in them in

various ways. It is based on the .NET Framework and it is highly

integrated with the rest of the Framework class library.

The ADO.NET API is designed so it can be used from all programminglanguages that target the .NET Framework, such as Visual Basic, C#,

J# and Visual C++.

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ADO.NET Data Architecture

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AccessingData In Connected Ado.Net

ArchitectureIn connected architecture database connection need to open andclose explicitly. While accessing data, the respective database

need to be connected.

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In disconnected architecture database connection not requireafter data has retrieved and stored into a dataset. We need tore-connect the database when we want to update anychanges into database, or require new updated data fromdatabase

Accessing Data In Disconnected

Ado.Net Architecture

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The Connection object creates the connection to the database.Microsoft Visual Studio .NET provides two types ofConnection classes. The Connection object contains all of the

information required to open a connection to the database.

Connection Object

Dim cnNorthwind as New

System.Data.SqlClient.SqlConnection("User ID=sa;

Password=2389; Initial Catalog=Northwind; Data

Source=London; Connection TimeOut=60;" )

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Command objects are used to execute commands to adatabase across a data connection. The Commandobjects can be used to execute stored procedures on

the database, or return complete tables directly.

Command Object

Dim sql As String = "SELECT UnitsInStock FROM

Products WHERE ProductID = @ProdID"

Dim cmdProducts As SqlCommand (sql, cnNorthwind)

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Command objects provide three methods that are used to

execute commands on the database: ExecuteNonQuery()

Executes commands that have no return values such asINSERT, UPDATE or DELETE

ExecuteScalar()

Returns a single value from a database query

ExecuteReader()

Returns a result set by way of a DataReader object

Command Object

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The DataReader object provides a forward-only, read-only,connected stream recordset from a database.

Because only one row is in memory at a time, the DataReader

provides the lowest overhead in terms of systemperformance but requires the exclusive use of an openConnection object for the lifetime of the DataReader.

DataReader Object

Dim rdrProducts As SqlDataReader

rdrProducts = cmdProducts.ExecuteReader()

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The DataAdapter is the class at the core of ADO .NET'sdisconnected data access. It is essentially the middlemanfacilitating all communication between the database and aDataSet. The DataAdapter is used either to fill a DataTable orDataSet with data from the database with it's Fill method.

After the memory-resident data has been manipulated, theDataAdapter can commit the changes to the database bycalling the Update method.

DataAdapter Object

Dim cnNorthwind As New SqlConnection()

Dim daProducts As New SqlDataAdapter(SELECT * FROM

Products,cnNorthwind)

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The dataset is a disconnected, in-memory representation of data. It can beconsidered as a local copy of the relevant portions of the database. TheDataSet is persisted in memory and the data in it can be manipulated andupdated independent of the database. When the use of this DataSet isfinished, changes can be made back to the central database for updating.

The data in DataSet can be loaded from any valid data source like MicrosoftSQL server database, an Oracle database or from a Microsoft Access

database.

DataSet Object

Dim dsCustomers As New DataSet()

daCustomers.Fill(dsCustomers, "Customers")

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1. Typed

2. Untyped

Typed dataset

Is derived from the DataSet class and has an associated XML schema, whichis created at the time of the creation of the dataset.

Can be customized after creation.

Supports Intellisense and auto-completion for the elements of the syntax whilewriting code.

Untyped dataset

Does not have any associated XML schema, therefore, the structure of anuntyped dataset is not known at the compile time.

Represents tables and columns as collections.

Does not support Intellisense and auto-completion for the elements of thesyntax.

DataSet Types

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DataSet Object