In this tutorial we will work with DataReader to retrieve data from a MS Access database.
First of all, a DataReader is an ADO.NET object that provides read-only, forward-only data faster than a DataAdapter. It’s a good choice over the other objects for read-only purpose.
Also, it’s forward-only, means you cant go back to previous data which was accessed. The cursor in DataReader goes from top to button by using the Method Read.
To fill a DataReader with Data, we are going to use the OleDbCommand object and execute the result onto it.
First, we need to create a MS Access Database, with the following table in it:
Table Name: Position
Fileds:
ID, Number, Primary Key
Position, Text(50)
And the code:
Public Sub SelectAll()
Dim cmd As New OleDb.OleDbCommand
Dim strconn As String = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\Users\Power\Desktop\db.mdb"
Dim reader As OleDb.OleDbDataReader
Dim conn As New OleDb.OleDbConnection(strconn)
cmd.CommandText = "select * from Positions"
' Set the connection for the OleDbCommand
cmd.Connection = conn
'Open the connection
conn.Open()
'Execute the OleDbCommand
reader = cmd.ExecuteReader()
'Read data from DataReader
While reader.Read
' Display data in a messagebox for testing purpose
MsgBox(reader.Item("Position").ToString)
End While
' Close the connection
conn.Close()
End Sub
Execute this code, what did you get? ;-)
