private async void btnFetch_Click_1(object sender, EventArgs e)
{
// fetch an existing tile
ITiler tiler = new Tiler();
var tile = await tiler.FetchTile(txtDir.Text, Int32.Parse(txtX.Text), Int32.Parse(txtX.Text), Int32.Parse(txtX.Text));
listBox1.Items.Add($"Tile returned. Size:{tile.Length}");
}
