How to update multiple row at time

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VB

MS-Access

Hi friends i want to update multiple rows at time

Here is my code

Dim a As Integer
                   Dim alar As New ArrayList
                   For a = 0 To DataGridView1.Rows.Count - 1
                       If DataGridView1.Rows(a).Cells(0).Selected = True Then

                           alar.Add(DataGridView1.Rows(a).Cells("cardno").Value)

                           DataGridView2.Rows.Add(DataGridView1.Rows(a).Cells(0).Value, DataGridView1.Rows(a).Cells(1).Value, DataGridView1.Rows(a).Cells(2).Value, DataGridView1.Rows(a).Cells(3).Value, DataGridView1.Rows(a).Cells(4).Value)
                       End If

                   Next
                   '--------------------------------------------------
                   Dim count As Integer = alar.Count

                   Dim dsfs = alar.Item(0).ToString
                   '---------------------------------------------------
                   For i = 0 To alar.Count - 1

                       dsfs = alar.Item(0).ToString
                       Dim cn As New OleDbConnection
                       Dim cmd As New OleDbCommand

                       cn.ConnectionString = My.Settings.trialConnectionString
                       cn.Open()
                       cmd.Connection = cn
                       cmd.CommandType = CommandType.Text
                       ' For i = 0 To DataGridView1.Rows.Count - 1
                       Dim ab As String
                       ab = DataGridView1.CurrentRow.Cells("cardno").Value
                       cmd.CommandText = "update voter set Castt='" & ToolStripComboBox1.Text & "' where cardno= '" & alar.Item(0).ToString & "'"
                       cmd.ExecuteNonQuery()

                       ' Next
                       cn.Close()
                   Next
                   If res > 0 Then
                       MsgBox("Record  Not Update")
                       al.Clear()
                   Else
                       MsgBox("Record  Update")
                   End If
                   'End If
                   '---------------Roemove selected row int gridview------------------'
                   Dim row As Integer
                   Dim selRow As New DataGridViewRow
                   Dim index As Integer
                   index = DataGridView1.SelectedRows.Item(0).Index
                   selRow = DataGridView1.Rows.Item(index)
                   DataGridView1.Rows.Remove(selRow)
                   row = row - 1

               End If
               ' MsgBox("Allocate Voter to " + ToolStripComboBox1.Text)
           End If

In this code only one record will update

Please help me........

Thanks in advance.......