如何从vb .net中的ms访问表中获取下一条记录

Question

i am working with a MCQ app in vb .net i want to fetch every record frrom MS ACCESS database table called Q_A....here is my code

Dim i As Integer = 0
    con = New OleDb.OleDbConnection
    con.ConnectionString = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=MCQ.accdb"
    Try
        Dim da As New OleDb.OleDbDataAdapter("SELECT * FROM Q_A ", con)
        If ds.Tables("Q_A").Rows.Count > 0 Then


            da.Fill(ds, "Q_A")
            lblQno.Text = ds.Tables("Q_A").Rows(i).Item(0).ToString()
            lblQuestion.Text = ds.Tables("Q_A").Rows(i).Item(1).ToString()
            rbtn1.Text = ds.Tables("Q_A").Rows(i).Item(2).ToString()
            rbtn2.Text = ds.Tables("Q_A").Rows(i).Item(3).ToString()
            rbtn3.Text = ds.Tables("Q_A").Rows(i).Item(4).ToString()
            rbtn4.Text = ds.Tables("Q_A").Rows(i).Item(5).ToString()

            i = i + 1


        End If

        con.Close()

    Catch ex As Exception
        MsgBox(ex.Message.ToString)
    End Try

but i am not able to fetch next row using this code..pls help me..thanks in advance

Answer 1

Where is this code being run? From a button Click? The code above would appear to only display the last row and then throw an exception as the index would go out of bounds after i becomes larger than the rowcount.

The i integer would need to be declared in a wider scope and with each movement to the next row, ensure that you are not out of bounds with the rowcount before proceeding.

For example if you were doing this from the click of a button you would:

Dim i as integer = 0
Do your database query and populate your dataset

Inside your Button Click Event
if i < rowcount then
    lblQno.Text = ds.Tables("Q_A").Rows(i).Item(0).ToString()
    lblQuestion.Text = ds.Tables("Q_A").Rows(i).Item(1).ToString()
    rbtn1.Text = ds.Tables("Q_A").Rows(i).Item(2).ToString()
    rbtn2.Text = ds.Tables("Q_A").Rows(i).Item(3).ToString()
    rbtn3.Text = ds.Tables("Q_A").Rows(i).Item(4).ToString()
    rbtn4.Text = ds.Tables("Q_A").Rows(i).Item(5).ToString()

    i = i + 1
end if

Since the ds is populated and i is declared in a wider scope it is accessible in this sub and all you need to do is check to ensure there are rows left and if so, display that row. Once it's displayed increment i for the next row so that when you click the button again, it has the value of the next row index.