DataGridViewでセルの値をチェックする方法

DataGridViewでセルの値をチェックする方法
VB.NET

Private Sub dgv1_CellValidating(ByVal sender As Object, _
    ByVal e As DataGridViewCellValidatingEventArgs) _
    Handles dgv1.CellValidating

    Dim dgv As DataGridView = DirectCast(sender, DataGridView)

    If e.RowIndex = dgv.NewRowIndex OrElse Not dgv.IsCurrentCellDirty Then
        Exit Sub
    End If

    If dgv.Columns(e.ColumnIndex).Name = "col1" AndAlso _
            e.FormattedValue.ToString() = "" Then
        dgv.Rows(e.RowIndex).ErrorText = "セルが未入力です"
        e.Cancel = True
    End If
End Sub

Private Sub dgv1_CellValidated(ByVal sender As Object, _
    ByVal e As DataGridViewCellEventArgs) _
    Handles dgv1.CellValidated

    Dim dgv As DataGridView = DirectCast(sender, DataGridView)
    dgv.Rows(e.RowIndex).ErrorText = Nothing
End Sub

C#

private void dgv1_CellValidating(object sender,
    DataGridViewCellValidatingEventArgs e)
{
    DataGridView dgv = (DataGridView)sender;

    if (e.RowIndex == dgv.NewRowIndex || !dgv.IsCurrentCellDirty)
    {
        return;
    }

    if (dgv.Columns[e.ColumnIndex].Name == "col1" &&
        e.FormattedValue.ToString() == "")
    {
        dgv.Rows[e.RowIndex].ErrorText = "未入力セルが存在します";
        e.Cancel = true;
    }
}

private void dgv1_CellValidated(object sender,
    DataGridViewCellEventArgs e)
{
    DataGridView dgv = (DataGridView)sender;
    dgv.Rows[e.RowIndex].ErrorText = null;
}