async void EditButtonClickedAsync(object sender, EventArgs e)
 {
     // BindingContext as EventViewModel
     var editPage = new PostEditPage(BindingContext as PostViewModel);
     await Navigation.PushAsync(editPage);
 }
 async void AddButtonClickedAsync(object sender, EventArgs e)
 {
     var editPage = new PostEditPage(new PostViewModel(null));
     // var editPage = new EventEditPage();
     await Navigation.PushAsync(editPage);
 }