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1UCN Technology: Computer Science: Autumn 2012
ADO.NET 2.0
• Architecture• DataReader • DataSet• Connection factory• Config file
3UCN Technology: Computer Science: Autumn 2012
Data Providers
• OLE DB:A COM object, that maps the OLE DB api to the DBMS' apiIs Microsoft propritary.
• ODBC: Works similar to a printer driver undependent of DBMS and OS
• .NET Data provider:A set of classes that implements a set of interfaces and abstract classes
• Some are provided by Microsoft and are installed with the .Net framework.
• Others are written by the DBMS provider
4UCN Technology: Computer Science: Autumn 2012
Microsoft Data Providers
• Data Provider Namespace Assembly• OLE DB System.Data.OleDb System.Data.dll• Microsoft SQL Server System.Data.SqlClient System.Data.dll• Microsoft SQL Server Mobile System.Data.SqlServerCe System.Data.SqlServerCe.dll• ODBC System.Data.Odbc System.Data.dll• Oracle System.Data.OracleClient System.Data.OracleClient.dll
MS Access
5UCN Technology: Computer Science: Autumn 2012
Other providers
• Data Provider Website• Firebird Interbase http://www.mono-project.com/Firebird_Interbase• IBM DB2 Universal Database http://www-306.ibm.com/software/data/db2• MySQL http://dev.mysql.com/downloads/connector/net/1.0.html• PostgreSQL http://www.mono-project.com/PostgreSQL• Sybase http://www.mono-project.com/Sybase• Oracle (proprietary) http://www.oracle.com/technology/tech/windows/odpnet/
index.html
6UCN Technology: Computer Science: Autumn 2012
Classes and Interfaces
• Object Base Class Implemented Interfaces
• Connection DbConnection IDbConnection - Connection• Command DbCommand IDbCommand - SQL command• DataReader DbDataReader IDataReader - Forward reader• DataAdapter DbDataAdapter IDataAdapter - Used with Dataset• Parameter DbParameter IDataParameter - Parameters for
Command• Transaction DbTransaction IDbTransaction - Transaction
7UCN Technology: Computer Science: Autumn 2012
Two ways of DB access
• Connected:
– Open connection.
– Read/Write access (select, insert, update and delete) using a Command object.
– When reading (select) a DataReader object is returned. A DataReader is an iterator (cursor) into the result table.
– Close Connection.
• Disconnected:
– Fill a DataSet object (a copy of a part of the database) using a DataAdapter.
– DataAdapter wraps SQL-statement(s).
– A DataSet object contains DataTable objects.
– DataTable objects contain collections of rows and columns.
8UCN Technology: Computer Science: Autumn 2012
Connection vs. Connectionless
• Connection:– Open Connection– Execute DB operations– Close Connection– Working on actual (live)
data– Other applications can not
access data.
Domæneklasser
SQL
Dataklasser
DB
9UCN Technology: Computer Science: Autumn 2012
Domæneklasser
SQL
Dataklasser
DB
• Connectionless:– Create a copy of a part of
the database– Execute DB operations on
the copy– Other applications may
change date– The copy may be come
inconsistent.
Connection vs. Connectionless
• Data are changed in the local copy:– at update it is checked if the data in the
database have been modified by others– in that case the update is rejected
(ConcurrencyException).
10UCN Technology: Computer Science: Autumn 2012
Overview of using databases
• 4 steps:
1. Open connection to database
2. Execute SQL for updating DB or fetching records
3. Handle data
4. Close connection
11UCN Technology: Computer Science: Autumn 2012
Step 1: Open Connection
• Connection are opened according to connection string info– here is a connection to a MS Access database opened– The database is located here: @"c:\AnyPlace\MyDb.mdb"– @ means that escape characters are discarded
<%@ import namespace="System.Data"%><%@ import namespace="System.Data.OleDb"%>
string sConnection;sConnection = "Provider=Microsoft.Jet.OLEDB.4.0;" + "Data Source="+@"c:\AnyPlace\MyDb.mdb");
OleDbConnection dbConn;dbConn = new OleDbConnection(sConnection);dbConn.Open();
connection
12UCN Technology: Computer Science: Autumn 2012
Open Connection
• Connections are opened using a connection string– May be found using Visual Studio:
// Create and open a connection. SqlConnection cn = new SqlConnection(); cn.ConnectionString = "Data Source=PCM06073\\SQLEXPRESS;”
+”Initial Catalog=vw;Integrated Security=True;"; cn.Open(); ShowConnectionStatus(cn);
// or should it be? cn.ConnectionString = “Server=PCM06073\\SQLEXPRESS;” +”Initial Catalog=vw;Integrated Security=True;"; cn.Open();
Data Sourceor
Server?
Server is preferable.
13UCN Technology: Computer Science: Autumn 2012
Connection Strings
• Connection strings are product specific (DB specific) anf often very well-documented.
• Help may be found at:– www.connectionstrings.com – www.able-consulting.com/ADO_conn.htm
14UCN Technology: Computer Science: Autumn 2012
Step 2: Get / fetch data
• Data are fetched by creating a Command object and use it to execute a SQL statement.
• Data can be stored in either a DataReader object or a DataSet object.
15UCN Technology: Computer Science: Autumn 2012
Differences between DataReader and DataSet/DataAdapter
• DataReader can only be used for reading data.• It can only be traversed once (forward).• DBCommand can update the database by ExecuteNonQuery. This
update is executed immediately.
• DataAdapter is the connection between DataSet and database.• Data are fetched to the DataSet, might be modified and sent back to
the database.• Updates are executed on a local copy. Concurrency problems must
be handled. • Possible to traverse forward and backward.• A DataSet can contain multiple tables.
16UCN Technology: Computer Science: Autumn 2012
Step 2: Get records Method 1: DataSet
• Get records by SQL Select query and DataAdapter– Data can be read and changed
string sql;sql = " Select lastname, firstname" + " From employee" + " Order By lastname Asc, firstname Asc;";
OleDbCommand dbCmd;dbCmd = new OleDbCommand(dbConn, sql);adapter.SelectCommand = dbCmd;dataset =new DataSet("MyTable");adapter.Fill(dataset); dataset
recordrecordrecord
17UCN Technology: Computer Science: Autumn 2012
Step 2: Get records Method 2: DataReader
• Get records via SQL Select query– read-only access to the database
string sql;sql = " Select lastname, firstname" + " From employee" + " Order By lastname Asc, firstname Asc;";
OleDbCommand dbCmd;dbCmd = new OleDbCommand(sql, dbConn);
OleDbDataReader dbReader;dbReader = dbCmd.ExecuteReader(); data reader
recordrecordrecord
18UCN Technology: Computer Science: Autumn 2012
What is achieved?
• We have created a connection to a database.
• The connection is placed in the connection object.
• We have done a search by using a SQL-statement.
• The search was executed by using a command object.
• The result of the search was stored in a DataSet or as here a DataReader object.
• Now it is possible to get the data from this object for viewing, passing on to client or handle in other ways.
• The following example shows how it can be done in a aspx file.
Example: ..\vwReader
19UCN Technology: Computer Science: Autumn 2012
Exercise
• Work through the rest of these slides and do this exercise:– Create a SQL Server Database with one table: studentList
• The table should have the following columns:id, fname, lname and email
• Enter some sample data into the table.– Create a ado.net connection ( in VS)
• And write an application that prints the table. – Modify the application by adding a class Student, so that an
object is used for representing a tuple.– Read Student objects from the database into an ArrayList
and a List<Student>.– Print fname + lname for the 3. element in both lists.– Create a new Student object and insert it into the database.
20UCN Technology: Computer Science: Autumn 2012
DataGrid• A simple example:
<%@ Page Language="C#" AutoEventWireup="true" %>
<%@ Import Namespace="System.Data" %><%@ Import Namespace="System.Data.OleDb" %>
Script kommer ind her.......
<html<head id="Head1" runat="server"> <title>Untitled Page</title></head><body> <form id="form1" runat="server"> <asp:DataGrid ID="MyDataGrid" runat="server"></asp:DataGrid> </form></body></html>
21UCN Technology: Computer Science: Autumn 2012
Datagrid (2)• The script by using DataReader:
<script runat="server"> OleDbDataReader data; protected void Page_Load(Object Src, EventArgs E) { String sConnection = "Provider=Microsoft.Jet.OLEDB.4.0;" + "Data Source=" + Server.MapPath("firma.mdb");
//Step 1: Open connection OleDbConnection dbConn = new OleDbConnection(sConnection); dbConn.Open();
//Step 2: Get data OleDbCommand dbCom = new OleDbCommand("select * from employee", dbConn); data = dbCom.ExecuteReader();
MyDataGrid.DataSource = data; MyDataGrid.DataBind(); }</script>
22UCN Technology: Computer Science: Autumn 2012
Datagrid (2)• The script by using DataSet:
<script runat="server"> OleDbDataReader data; protected void Page_Load(Object Src, EventArgs E) { String sConnection = "Provider=Microsoft.Jet.OLEDB.4.0;" + "Data Source=" + Server.MapPath("firma.mdb"); //Step 1: Open connection OleDbConnection dbConn = new OleDbConnection(sConnection); dbConn.Open(); //Step 2: Get data OleDbCommand dbCom = new OleDbCommand("select * from employee", dbConn);
OleDbDataAdapter adapter = new OleDbDataAdapter(); adapter.SelectCommand = dbCom; DataSet data = new DataSet(); adapter.Fill(data);
MyDataGrid.DataSource = data; MyDataGrid.DataBind(); }</script>
23UCN Technology: Computer Science: Autumn 2012
Factory
• Problem: Unlike ODBC, knowledge of the implementation might be spread to many places in the application.That's because of the set of dedicated classes
• The solution is to use a factory (from factory pattern)• In ADO.NET 2.0, it is implementet in the framework.
Otherwise you to implement it yourself (see Troelsen).
• A coupIe of examples follows:
1. Which .Net providers are available
2. Use factory to create a Connection and a Command object
Example: ..\adoDotNet\adoOpgave
24UCN Technology: Computer Science: Autumn 2012
Which .NET data providers are installed?
• The information is collected from machine.config
using System.Data;using System.Data.Common;.....DataTable dt = DbProviderFactories.GetFactoryClasses();foreach (DataRow dr in dt.Rows){
Console.WriteLine("{0}\t\t{1}\t\t{2}", dr[0], dr[1],dr[2]);}
Odbc Data Provider .Net Framework Data Provider for Odbc System.Data.OdbcOleDb Data Provider .Net Framework Data Provider for OleDb System.Data.OleDbOracleClient Data Provider .Net Framework Data Provider for Oracle System.Data.OracleClientSqlClient Data Provider .Net Framework Data Provider for SqlServer System.Data.SqlClient
25UCN Technology: Computer Science: Autumn 2012
Use factory to create Connection and Command objects
• Here is no references in the source code to concrete classes• provider and connectionString may be placed in the config file
string provider = "System.Data.OleDb";string connectionString = "Provider=Microsoft.Jet.OLEDB.4.0; Data Source=firma.mdb";DbProviderFactory factory= DbProviderFactories.GetFactory(provider);DbConnection conn=factory.CreateConnection();conn.ConnectionString=connectionString;conn.Open();Console.WriteLine(conn.State);
DbCommand command = factory.CreateCommand();command.CommandText = "SELECT * FROM employee";command.Connection = conn;DbDataReader dataReader = command.ExecuteReader();while (dataReader.Read()){
Console.WriteLine(dataReader[1]);}
26UCN Technology: Computer Science: Autumn 2012
Connection strings
• Connection strings depends on the provider and are not well documented
• Where to get help?– www.connectionstrings.com– www.carlprothman.net/Default.aspx?tabid=81– Providers documentation
• Visual Studio can generate some of them
27UCN Technology: Computer Science: Autumn 2012
.Config fil• Configuration files are used several places in .Net• i.e in ASP.NET for setting site properties and security• In Remoting for setting remote object properties• In ADO.NET to set provider and connection string• You might also use own application dependent properties• In a .Net application the config file should be called
<full assemblyname.config>, i.e test.exe.config or test.dll.config
• If you call it app.config in Visual Studio, it automatically copied and renamed when the application is built.
• In ASP.NET it must be named web.config. You might define one in different sub folders, but the security part (authentification e.g.) must be in the root folder of the site.
28UCN Technology: Computer Science: Autumn 2012
.config fil and ADO.NET
• Example of SQLExpress connection string:
<?xml version="1.0" encoding="utf-8" ?><configuration> <configSections> </configSections> <connectionStrings> <add name="TestConnection" connectionString="Data Source=pcm06463\sqlexpress;Initial Catalog=dbtest; User ID=test;Password=" providerName="System.Data.SqlClient" /> </connectionStrings></configuration>
Machine name
Nessesary for sqlexpress
Database
Internal name
29UCN Technology: Computer Science: Autumn 2012
Get provider and connection string
• From ConfigurationManager:
.... string provider = ConfigurationManager.ConnectionStrings["TestConnection"].ProviderName; string connStr = ConfigurationManager.ConnectionStrings["TestConnection"].ConnectionString;.....
30UCN Technology: Computer Science: Autumn 2012
A (nearly) complete example in ASP.NET protected void Page_Load(object sender, EventArgs e) { if (!IsPostBack) { string provider = ConfigurationManager.ConnectionStrings["TestConnection"].ProviderName; string connStr = ConfigurationManager.ConnectionStrings["TestConnection"].ConnectionString; DbProviderFactory factory = DbProviderFactories.GetFactory(provider); DbConnection conn = factory.CreateConnection(); conn.ConnectionString = connStr; conn.Open(); DbCommand command = factory.CreateCommand(); command.CommandText = "SELECT * FROM datotest"; command.Connection = conn;
DataSet ds = new DataSet("TestDataSet"); DbDataAdapter da = factory.CreateDataAdapter(); da.SelectCommand = command; da.Fill(ds); MitGitter.DataSource = ds; MitGitter.DataBind(); } }
31UCN Technology: Computer Science: Autumn 2012
The Aspx file
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" ><body> <form id="form1" runat="server"> <div> <asp:GridView ID="MitGitter" runat="server"/> </div> </form></body></html>
32UCN Technology: Computer Science: Autumn 2012
Parameters in SQL statements• Makes it possible to use the same SQL-statement in multible
situations.• But harder to debugge
string sqlString = "INSERT INTO datotest Values (@dato)"; SqlParameter sqlParam = new SqlParameter("@dato", System.Data.SqlDbType.DateTime); sqlParam.Value = DateTime.Now;
SqlCommand comm = _conn.CreateCommand(); comm.CommandText = sqlString; comm.Parameters.Add(sqlParam);
int result = comm.ExecuteNonQuery();ExecuteNonQuery is
used for insert, delete and update