1 Introduction to ADO.NET Microsoft ADO.NET 2.0 Step by Step Rebecca M Riordan Microsoft Press, 2006

2 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

3 The ADO.NET Object Model Adapter Command Reader Connection DataSet DATABASEDATABASE CLIENTCLIENT 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

4 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.

5 Data Provider Objects Connection Controls communication with data source Properties: ConnectionString Identifies server and database User ID and password (if external) Methods Open Close

6 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";

7 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

8 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.

9 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

10 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.

11 Table Adapter Includes a DataAdapter and a Connection object. Improves functionality and ease of use of the original DataAdapter.

12 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

13 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

14 The DataSet From ADO.NET 2.0 Step by Step

15 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

16 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.

17 The DataSet A DataSet object can exist independently of any database. We will only use DataSets to hold data retrieved from a database.

18 Summary DataAdapter Command DataReader Connection DataSet DATABASEDATABASE CLIENTCLIENT Data Provider ADO.NET