Ссылка на объект нулевой экземпляр объекта

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Imports System
Imports System.Collections.Generic
Imports System.ComponentModel
Imports System.Data
Imports System.Drawing
Imports System.Linq
Imports System.Text
Imports System.Windows.Forms
Public Class Form1

    Private Sub DataGridView1_CellBeginEdit(ByVal sender As System.Object, ByVal e As System.Windows.Forms.DataGridViewCellCancelEventArgs) Handles DataGridView1.CellBeginEdit
        Dim row As New DataGridViewRow
        For Each row In DataGridView1.Rows
            row.Cells(DataGridView1.Columns("total").Index).Value = (Convert.ToDouble(row.Cells(DataGridView1.Columns("todayattendence").Index).Value) + Convert.ToDouble(row.Cells(DataGridView1.Columns("oldattendence").Index).Value))
        Next
    End Sub

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        'TODO: This line of code loads data into the 'BanDataSet.Table1' table. You can move, or remove it, as needed.
        Me.Table1TableAdapter.Fill(Me.BanDataSet.Table1)

    End Sub

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        On Error GoTo saveErr
        Table1BindingSource.EndEdit()
        Table1TableAdapter.update(BanDataSet.Table1)
        MessageBox.Show("ok saved")
saveErr:

    End Sub

End Class

Что я уже пробовал:

я попытался обновить databasetable ms access через datagridview, но в datagridview есть одно условие один столбец + два столбца =третий столбец

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