Question

I’m kinda new to WPF. I’m making an app using WPF (all the UI controls are already fixed) and MVVM but most of the events are in the code-behind. I’m in the process of clearing the code-behind but I have codes like (the ones below) to switch through tabs, and to trigger visibility of controls depending on parameters:

tabItem1.Selected = true;

textBox1.Visibility = Visibility.Hidden;

lbxHusbandsWives.Items.Add(txtHusbandsWives.Text + '/' +
   cbxHusbandsWivesCountry.Text + '/' +
   dpHusbandsWives.SelectedDate.Value.ToShortDateString());

How can I do that in the viewmodel? Well, inside a Command? So I can clear the messy code-behind? Thanks for your help. 🙂

Answer 1

As I said many times before, MVVM doesn’t mean “no code behind”. There are things that you can or should do in code-behind, as long as they are strictly related to the view and are not necessary for the ViewModel to work properly.

That being said, in most cases you don’t need to do anything in code-behind. You normally use bindings to control the view from the ViewModel. This allows the ViewModel to be completely ignorant of the view: it just exposes properties that the view can access, and sends notifications when the values of the properties change. The ViewModel should definitely not manipulate the view or its components.

Everything in the code you posted can be done with bindings in XAML:

• textBox1.Visibility can be bound to a bool property of the ViewModel, using a BooleanToVisibilityConverter
• lbxHusbandsWives.ItemsSource can be bound to an ObservableCollection in the ViewModel (an ObservableCollection notifies the view when items are added to or removed from it)
• txtHusbandsWives.Text, cbxHusbandsWivesCountry.Text and dpHusbandsWives.SelectedDate can also be bound to properties of the appropriate type