' Forces the row to repaint itself when the user changes the 
' current cell. This is necessary to refresh the focus rectangle.
Sub dataGridView1_CurrentCellChanged(ByVal sender As Object, _
    ByVal e As EventArgs) Handles dataGridView1.CurrentCellChanged

    If oldRowIndex <> -1 Then
        Me.dataGridView1.InvalidateRow(oldRowIndex)
    End If
    oldRowIndex = Me.dataGridView1.CurrentCellAddress.Y

End Sub 'dataGridView1_CurrentCellChanged

// Forces the row to repaint itself when the user changes the 
// current cell. This is necessary to refresh the focus rectangle.
void dataGridView1_CurrentCellChanged(object sender, EventArgs e)
{
    if (oldRowIndex != -1)
    {
        this.dataGridView1.InvalidateRow(oldRowIndex);
    }
    oldRowIndex = this.dataGridView1.CurrentCellAddress.Y;
}