private async void AddTicket_ClickedAsync(object sender, System.EventArgs e)
{
var page = new AddTicketPage(TicketsViewModel.GetInstance());
await navigation.PushAsync(page);
}
private void DeleteAction_Clicked(object sender, System.EventArgs e)
{
var mi = ((MenuItem)sender);
TicketsViewModel.GetInstance().RemoveTicket(mi.CommandParameter.ToString());
}