public void ShowProgressBar(string title, string message, int max, int progress)
    {
        Device.BeginInvokeOnMainThread(() =>
        {
            dialog = new ProgressDialog(Plugin.CurrentActivity.CrossCurrentActivity.Current.Activity);
            dialog.SetTitle(title);
            //dialog.SetMessage(message);
            dialog.SetProgressStyle(ProgressDialogStyle.Horizontal);
            dialog.Max = max;
            dialog.Progress = 0;
            dialog.Show();
        });
    }

public void UpdateProgressBar(string message, int max, int progress)
    {
        Device.BeginInvokeOnMainThread(() =>
        {
            if (dialog != null)
            {
                  dialog.IncrementProgressBy(progress);
                  dialog.SetCanceledOnTouchOutside(false);
                  dialog.SetCancelable(false);
            }
        });
    }