Using ADO.NET Chapter Microsoft Visual Basic.NET: Reloaded 1

Using ADO.NET

Chapter Microsoft Visual Basic .NET: Reloaded

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Objectives

• Define the terms used when talking about databases

• Explain the purpose of the DataAdapter, Connection, and DataSet objects

• Explain the role of the provider

• Create and configure an OleDbDataAdapter object

• Write SQL SELECT statements

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Objectives (continued)

• Create a dataset

• Display a dataset in various controls in an interface

• Position the record pointer in a dataset

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Database Terminology• Database

• Organized collection of related information stored in a file on a disk

• Relational database stores information in tables composed of columns and rows

• Table is a group of related records• Each row represents a record• Each column represents a row

• Primary key is a field that uniquely identities a record in a table

• Foreign key is a field in one table used as the primary key in another table

• Tables are related by a common field or fields

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Database Terminology (continued)

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Database Terminology (continued)

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ADO.NET

• A Connection object is used to establish a temporary connection to a database

• Requests for information are then submitted using a DataAdapter object

• The DataAdapter uses a provider which translates the request into a language the database understands

• A DataSet stores a copy of the records and fields requested in a internal memory location

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ADO.NET (continued)

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ADO.NET (continued)

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Creating and Configuring a DataAdapter Object

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Creating and Configuring a DataAdapter Object (continued)

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Creating and Configuring a DataAdapter Object (continued)

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Creating and Configuring a DataAdapter Object (continued)

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Creating and Configuring a DataAdapter Object (continued)

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Creating and Configuring a DataAdapter Object (continued)

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SQL

• Structured Query Language (SQL)

• A set of commands that allows you to access and manipulate the data stored in many database management systems on computers of all sizes

• SELECT statement allow you to specify which fields and records you want to view

• WHERE clause limits records to be selected

• ORDER BY clause sorts record display order

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HOW TO…

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HOW TO… (continued)

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Using the Query Builder to Enter a SELECT Statement

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Using the Query Builder to Enter a SELECT Statement (continued)

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Using the Query Builder to Enter a SELECT Statement (continued)

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Using the Query Builder to Enter a SELECT Statement (continued)

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Using the Query Builder to Enter a SELECT Statement (continued)

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Using the Query Builder to Enter a SELECT Statement (continued)

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Using the Query Builder to Enter a SELECT Statement (continued)

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Creating a DataSet

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Creating a DataSet (continued)

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Creating a DataSet (continued)

• XML (Extensible Markup Language)

• XML schema definition file defines the tables and fields that make up the data set

• Schema file is automatically generated by VB.NET

• Contents of file may be viewed in IDE

• Contents of dataset can be preview by right clicking the DataAdapter object in the component tray and clicking Preview Data

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Creating a DataSet (continued)

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Using the Fill Method

• Method of the DataAdapter object• Fills a dataset with data while the application

is running

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Binding the Dataset Object to a DataGrid Control

• Connecting a DataSet object to a control is called “binding”

• Connected controls are referred to as “bound controls”

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HOW TO…

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Binding the Dataset Object to a DataGrid Control (continued)

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Reconfiguring the DataAdapter Object

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Reconfiguring the DataAdapter Object (continued)

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Reconfiguring the DataAdapter Object (continued)

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Binding the Dataset Object to a Label Control or Text box

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Binding the Dataset Object to a Label Control or Text box (continued)

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Binding the Dataset Object to a Label Control or Text box (continued)

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Binding the Dataset Object to a Label Control or Text box (continued)

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Programming Example – Cartwright Industries Application

• Carl Simons, the sales manager at Cartwright Industries, records the item number, name, and price of each product the company sells in a database named Items.mdb

• The database is contained in the VbDotNet\Chap12\Databases folder.

• Mr. Simons wants an application that the sales clerks can use to enter an item number and then display the item’s price

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Programming Example – Cartwright Industries Application (continued)

• Items.mdb database opened in Microsoft Access. Database contains one table tblItems

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TOE Chart

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User Interface

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Objects, Properties, and Settings

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Tab Order

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Pseudocode

btnExit Click event procedure

1. close application

frmCartwright Load event procedure

1. fill the dataset with the item numbers and prices from the Items.mdb database

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Code

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Summary• Databases created by Microsoft Access are

relational databases:• Can contain one or more tables

• Most tables contain a primary key that uniquely identifies each record

• Data in relational database can be displayed in any order, and you can control the amount of information you want to view

• Visual Basic .NET uses a technology called ADO.NET to access the data stored in a database

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Summary (continued)

• Connection between a database and an application that uses ADO.NET is only temporary

• To access data stored in a database, first create and configure a DataAdapter object, which is the link between the application and the Connection object

• Use an OleDbDataAdapter object and an OleDbConnection object in applications that access Microsoft Access databases

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Summary (continued)

• DataAdapter, Connection, and DataSet objects are stored in component tray

• Use SQL SELECT statement to specify fields and records for a dataset

• Query Builder provides a convenient way to create a SELECT statement

• Dataset contains data you want to access from the database

• Data specified in SELECT statement associated with DataAdapter object

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Summary (continued)

• Use DataAdapter object’s Fill method to fill a dataset with data while an application is running

• Users view data stored in a dataset through controls that are bound to DataSet object

• Use DataGrid control to display records contained in a dataset

• When you change the SELECT statement associated with a DataAdapter object, you must regenerate the dataset