24/02 Accessing DATA from a DataReader:

Date 24/2/11 Thursday

Accessing DATA from a DataReader: - DataReader is a class which hold Data in the form of Rows and Columns (Table Structure). To access the data from the DataReader, it provide us following methods.

1.      Read() à bool    (return type)

-          Moves the record pointer from current location to next Row and returns a status specifying, where the Row contains Data to which it has moved, that will be true if present or False if not present.

2.      GetValue(int index) à object

-          Used for retrieving field values from the row to which pointer was pointing by specific the column index position.

Note -  we can also access the row pointer by pointer in the form of single dimensional array also, either by specifying column index position or name, As following:

< DR > [index ]             à object < DR > [Colname]        à object

3.      GetName(int Index)   à String

-          Returns the name of column for given index position.

4.      NextResult()               à bool

-          Moved the record pointer from current table to next table if a table exists & returns true or else returns False.

Add a new form in the project:

Pics

-          Now write the following code:

using System.Data.OleDb;

Variable Declaration : OleDbConnection  con; OleDbcommand     cmd; OleDbDataReader   dr;

Under Form load : con = new OleDbConnection(“Provider=Msdaora; User ID = Scott; Password=tiger”); cmd = new OleDbcommand(“Select Deptno, Dname, Loc From Dept”, con); con.Open(); dr = cmd.ExecuteReader(); lable1.Text = dr.GetName(0); lable2.Text = dr.GetName(1); lable3.Text = dr.GetName(2); ShowData();

Define a method ShowData : Private void ShowData() {    If(dr.Read())    {       textBox1.Text = dr.GetValue(0).ToStrring();       textBox1.Text = dr[1].ToString();       textBox1.Text = dr[“Loc”].ToString();    } else    {          MessageBox.Show(“Last Record”    } }

Under next button : ShowData();

Under Close Button : If(con.state != ConnectionState.Closed) con.Class(); this.Close();