Question

I had a quick question on working with listboxes in WP7 using MVVM Light. Basically before I was using MVVM all I had to do was set the SelectedIndex to -1 inside of the OnNavigatedTo event when the page was navigated to. Then inside of the SelectionChanged event I would check if the SelectedIndex was equal to -1 and if so I would ignore it. The reason I did this was just in case the user wanted to select the same item again when they came back to the page.

Now with MVVM (MVVM Light) I’m binding the event to a command, which takes care of the first part. But now I’m stuck because I don’t know how to set the SelectedIndex to -1 from the ViewModel which prevents the user from selecting the same item again. Any ideas?

Answer 1

Try creating a SelectedItem property on your viewmodel, then do a two-way between the SelectedItem viewmodel property and the SelectedItem property on your ListBox. Then you can update it with whatever value you want when your Command fires and the result will propagate back to your ListBox.