VB.Net/Database ADO.net/OleDbDataReader

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Версия от 15:44, 26 мая 2010; Admin (обсуждение | вклад) (1 версия)
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Use OleDbDataReader to read data

<source lang="vbnet"> Imports System Imports System.Data Imports System.Data.OleDb Imports System.Data.SqlClient Imports System.Collections Imports System.Windows.Forms Imports System.Resources Public Class MainClass

   Shared Sub Main()
       "Declare variables and objects
       Dim strConnectionString As String = _
           "Provider=Microsoft.Jet.OLEDB.4.0;" & _
           "Data Source=Employee.mdb;"
       Dim objConnection As New OleDbConnection(strConnectionString)
       Dim strSQL As String = "SELECT * FROM Employee"
       Dim objCommand As New OleDbCommand(strSQL, objConnection)
       Dim objDataAdapter As New OleDbDataAdapter(objCommand)
       Dim objDataTable As New Data.DataTable("Employee")
       Dim objDataRow As DataRow
       Try
           "Open the database connection
           objConnection.Open()
       Catch OleDbExceptionErr As OleDbException
           "Write the exception
           Console.WriteLine(OleDbExceptionErr.Message)
       Catch InvalidOperationExceptionErr As InvalidOperationException
           "Write the exception
           Console.WriteLine(InvalidOperationExceptionErr.Message)
       End Try
       "Declare an OleDbDataReader object
       Dim objDataReader As OleDbDataReader
       Try
           "Execute the SQL text
           objDataReader = objCommand.ExecuteReader()
           "Check to see if we have data
           If objDataReader.HasRows Then
               "Process all rows
               While objDataReader.Read()
                   "Get the data in each column
                   For intIndex As Integer = 0 To objDataReader.FieldCount - 1
                       Console.WriteLine( objDataReader.Item(intIndex).ToString & ", ")
                   Next
               End While
           End If
           "Close the reader
           objDataReader.Close()
       Catch OleDbExceptionErr As OleDbException
           Console.WriteLine(OleDbExceptionErr.Message)
       End Try


       "Close the database connection
       objConnection.Close()
       "Clean up
       objDataRow = Nothing
       objDataTable.Dispose()
       objDataTable = Nothing
       objDataAdapter.Dispose()
       objDataAdapter = Nothing
       objCommand.Dispose()
       objCommand = Nothing
       objConnection.Dispose()
       objConnection = Nothing
   End Sub

End Class

      </source>

<A href="http://www.vbex.ru/Code/VBDownload/Employee.zip">Employee.zip( 7 k)</a>


Use OleDbDataReader to read data from "select" command

<source lang="vbnet"> Imports System Imports System.Data Imports System.Data.OleDb public class MainClass

  Shared Sub Main()
     "Create Connection object
     Dim thisConnection As New OleDbConnection _
        ("Provider=Microsoft.Jet.OLEDB.4.0;" & _
         "Data Source=Employee.mdb")
     "Create Command object
     Dim thisCommand As New OleDbCommand _
        ("SELECT ID, FirstName FROM Employee", _
         thisConnection)
     Try
        " Open Connection
        thisConnection.Open()
        Console.WriteLine("Connection Opened")
        " Execute Query
        Dim thisReader As OleDbDataReader = thisCommand.ExecuteReader()
        While (thisReader.Read())
           Console.WriteLine("FirstName: {0} {1}", _
              thisReader.GetValue(0), thisReader.GetValue(1))
        End While
     Catch ex As OleDbException
        " Display error
        Console.WriteLine("Error: " & ex.ToString())
     Finally
        " Close Connection
        thisConnection.Close()
        Console.WriteLine("Connection Closed")
     End Try   
  End Sub

End Class

      </source>

<A href="http://www.vbex.ru/Code/VBDownload/Employee.zip">Employee.zip( 7 k)</a>