private void ThumbnailXpress_KeyDown_handler(object sender, KeyEventArgs e)
{
    Accusoft.ThumbnailXpressSdk.ThumbnailXpress txtemp = (Accusoft.ThumbnailXpressSdk.ThumbnailXpress)sender; 
    ThumbnailItem TITemp; 
    if (e.KeyCode == Keys.Down || e.KeyCode == Keys.Right)
    {
        //select the next thumbnail item
        TITemp = txtemp.SelectedItems[txtemp.SelectedItems.Count - 1]; 
        txtemp.SelectedItems.Add(txtemp.Items[txtemp.Items.IndexOf(TITemp) + 1]); 
        txtemp.ScrollItems(ScrollItemsType.ItemIndex, txtemp.Items.IndexOf(TITemp)); 
    }
    else if (e.KeyCode == Keys.Left || e.KeyCode == Keys.Up)
    {
        //select the previous thumbnail item
    }
            
}