private async void ToolbarItem_Clicked(object sender, EventArgs e)
{
var editPage = new EditPage();
editPage.SetData(null);
await Navigation.PushAsync(editPage);
}
private async void ListViewElementi_ItemTapped(object sender, ItemTappedEventArgs e)
{
var item = (DbItem)(e.Item);
var editPage = new EditPage();
editPage.SetData(item);
await Navigation.PushAsync(editPage);
}