Chapter Six
Database Programming
Ado.net
Introducing ADO.Net
Most of today's applications need to interact with database systems to persist, edit or view data.
In .Net, data access services are provided through ADO.Net components. ADO.Net is an object
oriented framework that allows you to interact with database systems.
We usually interact with database systems through SQL queries or stored procedures. The best
thing about ADO.Net is that it is extremely flexible and efficient. ADO.Net also introduces the
concept of a disconnected data architecture.
The application stays connected to the DB system even when it is not using DB services. This
commonly wastes valuable and expensive database resources, as most of the time applications
only query and view the persistent data. ADO.Net solves this problem by managing a local
buffer of persistent data called a data set.
Your application automatically connects to the database server when it needs to run a query and
then disconnects immediately after getting the result back and storing it in the dataset. This
design of ADO.Net is called a disconnected data architecture and is very much similar to the
connectionless services of HTTP on the internet. It should be noted that ADO.Net also provides
connection oriented traditional data access services.
Different components of ADO.Net
Before going into the details of implementing data access applications using ADO.Net, it is
important to understand its different supporting components or classes. All generic classes for
data access are contained in the System. Data namespace.
Class
Description
Dataset: the Dataset is a local buffer of tables or a collection of disconnected record sets.
Data Table: A Data Table is used to contain data in tabular form using rows and columns.
Data Row: Represents a single record or row in a Data Table.
Data Column: - Represents a column or field of a Data Table.
Data Relation: - Represents the relationship between different tables in a data set..
Constraint : - Represents the constraints or limitations that apply to a particular field or column.
ADO.Net also contains some database specific classes. This means that different database system
providers may provide classes (or drivers) optimized for their particular database system.
Microsoft itself has provided the specialized and optimized classes for their SQL server database
system. The name of these classes start with 'Sql' and are contained in the System.Data.SqlClient
namespace.
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Similarly, Oracle has also provides its classes (drivers) optimized for the Oracle DB System.
Microsoft has also provided the general classes which can connect your application to any OLE
supported database server. The name of these classes start with 'OleDb' and these are contained
in the System.Data.OleDb namespace. In fact, you can use OleDb classes to connect to SQL
server or Oracle database; using the database specific classes.
Class
Description
SqlConnection, OleDbConnection ->represents a connection to the database system.
SqlCommand, OleDbCommand ->Represents SQL query.
SqlDataAdapter, OleDbDataAdapter ->A class that connects to the database system, fetches the
record and fills the dataset.
SqlDataReader, OleDbDataReader ->A stream that reads data from the database in a connected
design.
SqlParameter, OleDbParameter-> represents a parameter to a stored procedure.
THE ARCHITECTURE OF ADO.NET
Ado.net architecture
Performing common data access tasks with ADO.Net
Now we will build an application to demonstrate how common data access tasks are performed
using ADO.Net. We will use the MS SQL server and MS Access database systems to perform
the data access tasks. SQL Server is used because probably most of the time you will be using
MS SQL server when developing .Net applications.
For SQL server, we will be using classes from the System.Data.SqlClient namespace. Access is
used to demonstrate the OleDb databases. For Access we will be using classes from the
System.Data.OleDb namespace.
Accessing Data using ADO.Net
Data access using ADO.Net involves the following steps:
I. .Defining the connection string for the database server.
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II. Defining the connection (SqlConnection or OleDbConnection) to the database using the
connection string.
III. Defining the command (SqlCommand or OleDbCommand) or command string that contains
the query
IV Defining the data adapter (SqlDataAdapter or OleDbDataAdapter) using the command string
and the connection object.
V. Creating a new Dataset object
VI. If the command is SELECT, filling the dataset object with the result of the query through the
data adapter.
VII. Reading the records from the Data Tables in the datasets using the Data Row and Data
Column objects
VIII .If the command is UPDATE, INSERT or DELETE, then updating the dataset through the
data adapter
X. Accepting to save the changes in the dataset to the database
Since we are demonstrating an application that uses both SQL Server and Access databases we
need to include the following namespaces in our application:
using System.Data;
using System.Data.OleDb;
// for Access database
using System.Data.SqlClient; // for SQL Server
Defining the connection string
The connection string defines which database server you are using, where it resides, your user
name , password and the database name.
For SQL Server, we have written the following connection string:
// for Sql Server
string connectionString = "server= SQLEXPRESS; database=student; un=s; pwd=;";
First of all we have defined the instance name of the server, which is SQLEXPRESS on my
system. Next we defined the name of the database, user name (un) and password (pwd). Since
my SQL server doesn't have a password for the System Administrator (sa) user, I have left it
blank in the connection string.
// for MS Access
string connectionString = "provider=Microsoft.Jet.OLEDB.4.0;data source = c:\min \stud.mdb";
First we have defined the provider of the access database. Then we have defined the data source
which is the address of the target database.
Defining a Connection
a connection is defined using the connection string. This object is used by the data adapter to
connect to and disconnect from the database For SQL Server the connection is created like this:
// for Sql Server
SqlConnection conn = new SqlConnection (connectionString);
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And for Access the connection is created like this:
// for MS Access
OleDbConnection conn = new OleDbConnection(connectionString);
Defining the command or command string
The command contains the query to be passed to the database. Here we are using a command
string. We will see the command object (SqlCommand or OleDbCommand) later in the lesson.
The command string we have used in
our application is:
string commandString = "SELECT * from student";//stdent is table name
Defining the Data Adapter
For SQL Server, the data adapter is created like this:
// for Sql Server
SqlDataAdapter dataAdapter = new SqlDataAdapter(commandString, conn);
And for Access, the data adapter is created like this:
// for MS Access
OleDbDataAdapter dataAdapter = new OleDbDataAdapter(commandString, conn);
Creating and filling the DataSet
Finally we need to create an instance of the DataSet. As we mentioned earlier, a DataSet is a
local & offline container of data. The DataSet object is created simply:
DataSet ds = new DataSet();
Now we need to fill the DataSet with the result of the query. We will use the dataAdapter object
for this purpose and call its Fill() method. dataAdapter.Fill(ds, "stud");
Here we have called the Fill() method of dataAdapter object. We have supplied it the dataset to
fill and the name of the table (DataTable) in which the result of query is filled.
This is all we need to connect and fetch data from the database. Now the result of the query is
stored in the dataset object in the stud table, which is an instance of the DataTable. We can get a
reference to this table by using the indexer property of the dataset object's Tables collection.
DataTable dataTable = ds.Tables["stud"];
The indexer we have used takes the name of the table in the dataset and returns the
corresponding DataTable object. Now we can use the tables Rows and Columns collections to
access the data in the table.
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Example1: Program to Insert data into a table using C#.net
public partial class main : Form
{
OleDbConnection con = new OleDbConnection();
public main()
{
InitializeComponent();
con.ConnectionString=(@"provider=Microsoft.Ace.OLEDB.12.0;data source =
C:\Users\min\Documents\mmm.accdb");
}
private void button1_Click(object sender, EventArgs e){
try{
con.Open();
OleDbCommand cmd = new OleDbCommand();
cmd.Connection = con;
cmd.CommandText = "insert into student(fname,mname,lname) values('" + textBox1.Text +
"','" + textBox2.Text + "','" + textBox3.Text + "')";
cmd.ExecuteNonQuery();
MessageBox.Show("successfull");
con.Close();}
catch (Exception ex){
MessageBox.Show("error" + ex);}}}
Example1: Program to Insert data into a table using vb.net
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles
Button1.Click
Dim s As String = "Data Source=. \SQLEXPRESS;Initial
Catalog=Sample;Integrated Security=True"
Dim con As SqlClient. SqlConnection = New
SqlClient. SqlConnection(s)
con.Open()
Dim i As String = "insert into student values(" + "'" +
Me.TextBox1.Text + "'" + "," + "'" + Me.TextBox2.Text + "'" + "," + "'" +
Me.TextBox3.Text + "'" + ");"
Dim cmd As SqlClient. SqlCommand = New SqlClient. SqlCommand(i, con)
cmd.ExecuteNonQuery()
con.Close()
MsgBox("Data Inserted", vbInformation, "Save")
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Example2: Program to update data from a table using C# .net
public partial class main : Form{
OleDbConnection con = new OleDbConnection();
public main()
{
InitializeComponent();
con.ConnectionString=(@"provider=Microsoft.Ace.OLEDB.12.0;data source =
C:\Users\min\Documents\mmm.accdb");
}
private void button1_Click(object sender, EventArgs e)
{
try
{
conn.Open();
OleDbCommand cmd = new OleDbCommand();
cmd.Connection = conn;
string query ="update student set sal='" +textBox2.Text + "'where ID=" + textBox5.Text +
"";
cmd.CommandText = query;
cmd.ExecuteNonQuery();
MessageBox.Show("Data edited");
conn.Close();
}
catch (Exception ex){
MessageBox.Show("Error" + ex);}}
Example2: Program to update data from a table using vb.net
Private Sub Button4_Click(sender As Object, e As EventArgs) Handles
Button4.Click
Dim s As String = "Data Source=. \SQLEXPRESS;Initial
Catalog=Sample;Integrated Security=True"
Dim con As SqlClient. SqlConnection = New
SqlClient. SqlConnection(s)
con.Open()
Dim i As String = "update student set Sno=" + "'" + Me.TextBox4.Text
+ "'" + " where sno=" + "'" + Me.TextBox1.Text + "'" + ";"
Dim cmd As SqlClient. SqlCommand = New SqlClient. SqlCommand(i, con)
cmd.ExecuteNonQuery()
con.Close()
MsgBox("Data Updated", vbInformation, "Update")
End Sub
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Example 3: Program to Delete data from a table using C#.net
public partial class main : Form
{
OleDbConnection con = new OleDbConnection();
public main(){
InitializeComponent();
con.ConnectionString=(@"provider=Microsoft.Ace.OLEDB.12.0;data source =
C:\Users\min\Documents\mmm.accdb");
}
private void button1_Click(object sender, EventArgs e)
{
Try{
conn.Open();
OleDbCommand cmd = new OleDbCommand();
cmd.Connection = conn;
string query = "delete from student where ID=" + textBox5.Text + "";
cmd.CommandText = query;
cmd.ExecuteNonQuery();
MessageBox.Show("Data Deleted");
conn.Close();
}
catch (Exception ex)
{
MessageBox.Show("Error" + ex);}}
Example 3: Program to Delete data from a table using VB.net
Private Sub Button3_Click(sender As Object, e As EventArgs) Handles
Button3.Click
Dim s As String = "Data Source=. \SQLEXPRESS;Initial
Catalog=Sample;Integrated Security=True"
Dim con As SqlClient. SqlConnection = New
SqlClient. SqlConnection(s)
con.Open()
'Dim x As Integer = CInt(Me.TextBox1.Text)
Dim i As String = "delete from student where sno=" + "'" +
Me.TextBox1.Text + "'" + ";"
Dim cmd As SqlClient. SqlCommand = New SqlClient. SqlCommand(i, con)
cmd.ExecuteNonQuery()
con.Close()
MsgBox("Data deleted", vbInformation, "Delete")
End Sub
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Example 4: Program to search data from a table using C#.net
public partial class main : Form
{
OleDbConnection con = new OleDbConnection();
public main(){
InitializeComponent();
con.ConnectionString=(@"provider=Microsoft.Ace.OLEDB.12.0;data source =
C:\Users\min\Documents\mmm.accdb");
}
try
{
conn.Open();
OleDbCommand cmd = new OleDbCommand();
cmd.Connection = conn;
string query = "Select * from student where ID = "+textBox1.Text+"";
cmd.CommandText = query;
OleDbDataAdapter da = new OleDbDataAdapter(cmd);
DataTable dt = new DataTable();
da.Fill(dt);
dataGridView1.DataSource = dt;
conn.Close();
}
catch (Exception ex)
{
MessageBox.Show("erorr" + ex);}}
Example 4: Program to search data from a table using VB.net
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles
Button1.Click
Dim connection As SqlConnection = New sqlconnection()
connection. ConnectionString = "Data Source=PRABHU-DESKTOP; _
Initial Catalog=testDB;Integrated Security=True"
connection. Open()
Dim adp As SqlDataAdapter = New SqlDataAdapter _
("select * from stud", connection)
Dim ds As DataSet = New DataSet()
adp. Fill(ds)
DataGridView1. DataSource = ds. Tables(0)
End Sub
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