private void BtnSave_Click(object sender, EventArgs e)
{
chartLayout.DrawingCacheEnabled = true;
chartLayout.BuildDrawingCache(true);
chartbitmap = chartLayout.GetDrawingCache(true).Copy(Config.Rgb565, false);
chartLayout.DestroyDrawingCache();
var storage = Android.OS.Environment.ExternalStorageDirectory.AbsolutePath;
var filePath = System.IO.Path.Combine(storage, "Chart.png");
var stream = new FileStream(filePath, FileMode.Create);
chartbitmap.Compress(CompressFormat.Png, 100, stream);
stream.Close();
var alert = new AlertDialog.Builder(this);
alert.SetTitle("A Graph has been saved");
alert.SetMessage("File is located at: " + filePath.ToString());
alert.Show();
}