ODP.NET - Retrieving Data Using OracleDataReader

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Using keyword in Visual Basic 2005

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Using 'Using' for Simplicity

The above program can be made simple by using the Using statement together with ODP.NET classes as follows:

Sample Code

Using cn As New OracleConnection("Data Source=xe;
User Id=scott;Password=tiger")
Try
cn.Open()
Dim SQL As String
SQL = String.Format("SELECT ename, sal,
job FROM emp WHERE empno={0}", Me.txtEmpno.Text)
Using cmd As New OracleCommand(SQL, cn)
Using rdr As OracleDataReader = cmd.ExecuteReader
If rdr.HasRows Then
'read the first row
rdr.Read()
'extract the details
Me.txtEname.Text = rdr("ename")
Me.txtSal.Text = rdr("sal")
Me.txtJob.Text = rdr("job")
Else
'display message if no rows found
MessageBox.Show("Not found")
End If
End Using
End Using
Catch ex As Exception
MessageBox.Show("Error: " & ex.Message)
If cn.State = ConnectionState.Open Then
cn.Close()
End If
End Try
End Using

The Using keyword is new in Visual Basic 2005, which internally generates try and finally blocks around the object being allocated and calls Dispose() for you saving you the hassle of manually creating it.

The objects created using the Using keyword are automatically erased (and respective resources would be automatically cleared) from the memory once it is out of using scope. Even though it is very flexible to use the Using statement, for the sake of clarity, we will go without using it in the examples of this book.

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