ADO.NET.NET Data Access and Manipulation Mechanism. Nikita Gandotra Assistant Professor, Department of Computer Science & IT

Transcription

1 ADO.NET.NET Data Access and Manipulation Mechanism Nikita Gandotra Assistant Professor, Department of Computer Science & IT

2 Overview What is ADO.NET? ADO VS ADO.NET ADO.NET Architecture ADO.NET Core Objects Different ways for Data Access Steps of Data Access Using command, DataReader & DataAdapter object

3 What is ADO.NET? A data-access technology that enables applications to connect to data stores and manipulate data contained in them in various ways Former version was ADO (ActiveX Data Object) Using ADO, a connection is opened to the database, and some data is selected and placed into a record set consisting of fields; that data is then manipulated and updated on the server, and the connection is closed. tightly coupled to client server architectures Needs COM marshalling to pass data between tiers Connections and locks are typically persisted

4 Objective of ADO.NET Support disconnected data architecture, Tight integration with XML, Common data representation Ability to combine data from multiple and varied data sources Optimized facilities for interacting with a database

5 ADO / ADO.Net Comparisons Feature ADO ADO.Net In memory data storage Recordset object Mimics single table Dataset object Contains DataTables Data Reads Sequential Sequential or nonsequential Data Sources OLE/DB via the Connection object Managed provider calls the SQL APIs

6 ADO / ADO.Net Comparisons Feature ADO ADO.Net Disconnected data Limited support, suitable for R/O Strong support, with updating Passing datasets COM marshalling DataSet support for XML passing Scalability Limited Disconnected access provides scalability

7 ADO.NET Architecture

8 ADO.NET Core Objects Core namespace: System.Data.NET Framework data providers: Data Provider SQL Server OLE DB ODBC Oracle Namespace System.Data.SqlClient System.Data.OleDb System.Data.Odbc System.Data.OracleClient

9 ADO.NET Core Objects Object Connection Command DataReader DataAdapter DataTable DataSet Description Establishes a connection to a specific data source. (Base class: DbConnection) Executes a command against a data source. Exposes Parameters and can execute within the scope of a Transaction from a Connection. (The base class: DbCommand) Reads a forward-only, read-only stream of data from a data source. (Base class: DbDataReader) Populates a DataSet and resolves updates with the data source. (Base class: DbDataAdapter) Has a collection of DataRows and DataColumns representing table data, used in disconnected model Represents a cache of data. Consists of a set of DataTables and relations among them

10 Pros and Cons Connected Disconnected Database Resources - + Network Traffic - + Memory Usage + - Data Access - +

11 Different ways of Data Access SqlCommand ExecuteReader ExecuteNonQuery ExecuteScalar ExecuteXMLReader SqlDataAdapter DataSet

12 General Steps of Data Access 1. Defining the connection string 2. Defining the connection 3. Defining the command object 4. Open connection 5. Execute method 6. Close connection

13 Using the command object SqlCommand is used for connection to SQLSERVER Has Multiple constructors : New() New(cmdText) New(cmdText, connection)

14 Using the command object 1. string connstr="data Source=.;Initial Catalog=mcaclass;User ID=SA;Password=hello1234"; 2. string sql = "Select Name from tbl_details"; 3. SqlConnection sqlcnn = new SqlConnection(connStr); 4. try 5. { 6. sqlcnn.open(); 7. SqlCommand sqlcmd = new SqlCommand(sql, sqlcnn); 8. int val=sqlcmd.xecutequery(): 9. sqlcnn.close(); 10.}

15 Command Methods Command class core methods: ExecuteNonQuery : Executes a SQL statement against a connection object ExecuteReader: Executes the CommandText against the Connection and returns a DbDataReader ExecuteScalar: Executes the query and returns the first column of the first row in the result set returned by the query

16 The DataReader object DataReader objects are highly optimised for fast, forward only enumeration of data from a data command DataReader is not disconnected Access to data is on a per record basis. Forward only Read only Does support multiple recordsets

17 Using DataReader SqlDataReader sqlreader; sqlreader = sqlcommand.executereader(); while (sqlreader.read()) { } // process data sqlreader.dispose();

18 DataSets(using dataadapters) In-memory representation of data contained in a database/xml Operations are performed on the DataSet, not the data source Can be created programmatically, using a DataAdapter or XML schema and document (or any mixture)

19 DataAdapters Interface between DataSets and data sources Disconnected by design Supports select, insert, delete, update commands and methods Must always specify a select command All other commands can be generated or specified Compartively slower than DataReader

20 Using the DataAdapter SQLDataAdapter sqlda = new SqlDataAdapter(); sqlda.selectcommand = new SqlCommand ("select * from authors, sqlconnection); DataSet sqlds = new DataSet("authorsTable"); sqlda.fill(sqlds, "authorstable");