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Introduction to ADO.NET

Microsoft ADO.NET 2.0 Step by StepRebecca M RiordanMicrosoft Press, 2006

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Introduction to ADO.NET

“Active Data Objects”

A set of class defintions included in the .NET Framework

Objects collaborate to provide .NET applications (relatively) easy access to databases.

Designed for scalability. 100’s or 1000’s of clients on a database

server Offload functionality from server to client

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The ADO.NET Object Model

Adapter

Command

Reader

Connection

DataSetD

A

T

A

B

A

S

E

C

L

I

E

N

T

Data Provider

ADO.NET

Handles communication with a physical data store.

The actual data

Knows how to do SQL commands on the database

A light weight object for sequential read-only access to a query result.

Provides general disconnected access to data

http://msdn.microsoft.com/en-us/library/a6cd7c08.aspx

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Data Provider

Collection of Class Definitions Specific to a data source

MS SQL Server Oracle (others)

Same set of classes for each data source Class name differs

SqlDataConnection vs OracleDataConnection SqlCommand vs OracleCommand etc.

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Data Provider Objects

Connection Controls communication with data

source Properties:

ConnectionString Identifies server and database User ID and password (if external)

Methods Open Close

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Connection String

MS SQL Server Examples

connStr = "server=scorpius.eng.usf.edu; User ID=turnerr; Password=xxxxxxx"

connStr = "server=mssql06.discountasp.net; database=DB_110074;

User ID=rollinsturn; Password=xxxxx"

connStr = "server=(local)\\VSDOTNET; database=Bulk_Mail_Addresses; Trusted_Connection=yes";

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Data Provider Objects

Command Object Knows how to execute a SQL command on a server

Properties: CommandText

A SQL statement to be executed at the data source. SqlCommand1.CommandText = "SELECT * FROM Address_List"; Can be changed by the program.

Methods ExecuteReader ExecuteScalar ExecuteNonquery

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Data Provider Objects

DataReader

A fast, low-overhead object, similar to a StreamReader for file input.

Provides forward-only, read-only stream of data from a data source

Created by calling the ExecuteReader method of a Command object Never with “new”

Connection must remain open while the DataReader is used.

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Data Provider Objects

There are two kinds of “Adapters”

Data Adapter Present in ADO 1.0 Continued in ADO 2.1

Table Adapter New in ADO 2.0

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DataAdapter

Provides access to a collection of data from a data source Pemits client to close connection while

processing the data. Effectively provides a local cache Client accesses the cache rather than the

actual database.

Actual database can be updated when desired.

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Table Adapter

Includes a DataAdapter and a Connection object.

Improves functionality and ease of use of the original DataAdapter.

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Data Provider Objects

DataAdapter

Contains four Command Objects: SelectCommand UpdateCommand InsertCommand DeleteCommand

Uses SelectCommand to fill a DataSet Uses other command objects to

transmit changes back to the data source

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The DataSet

In-memory copy of data

No connection to a database. No knowledge of source or destination

of that data that it contains.

Simple form of relational database Has a collection of tables Has a collection of DataRelations

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The DataSet

From ADO.NET 2.0 Step by Step

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The DataSet

The DataTable Columns

Like the column defintions from a SQL CREATE TABLE statement

Name, Data Type, Max Length, Allows Nulls

Rows The data

Constraints Foreign Key Unique

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The DataSet

Data Relation

Programmatic interface for navigating from a master row in one table to related rows in another.

Example: Order ID in an Invoice to matching Order IDs in all Line Items for that invoice.

Does not enforce referential integrity A foreign key constraint does that.

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The DataSet

A DataSet object can exist independently of any database.

We will only use DataSets to hold data retrieved from a database.

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Summary

DataAdapter

Command

DataReader

Connection

DataSetD

A

T

A

B

A

S

E

C

L

I

E

N

T

Data Provider

ADO.NET