WPF ListBox send SelectedItem value to the viewmodel

Question

Inside MainWindow there is listbox filled with some data. These data is loaded from viewmodel, so I dont have any codebehind.

MainWindow.xaml

<ListBox Name="listBoxData" 
         DataContext="{Binding Source={StaticResource MainWindowViewModelDataSource}}" 
         ItemTemplate="{DynamicResource BookTemplate}"                              
         ItemsSource="{Binding Books}" />

How can I know which book is selected inside listbox (using ICommand ) and send it's property ( int Id for example) to viewmodel for further processing?

Answer 1

Simply bind SelectedItem to some property (say SelectedBook ) in your ViewModel, no need to have ICommand for this.

<ListBox Name="listBoxData" 
         ItemTemplate="{DynamicResource BookTemplate}"  
         ItemsSource="{Binding Books}"
         SelectedItem="{Binding SelectedBook}" />

You can get Id for the book by simply accessing ViewModel property:

int selectedBookId = SelectedBook.Id;

Answer 2

Add a SelectedBook property to your ViewModel class, preferably of your Book type.

Then in your XAML, add the proper Binding :

<ListBox SelectedItem="{Binding SelectedBook}"/>

If it acts up, you can force it to be a TwoWay binding, like so:

<ListBox SelectedItem="{Binding SelectedBook, Mode=TwoWay}"/>

It is imperative that your SelectedBook property also invoke the proper PropertyChanged notification so the binding keeps the UI and ViewModel in sync.

Answer 3

Rohit is right

bind the selected item of the listbox to a property that is in the viewmodel:

like this: (using a property called SelectedBook)

 <ListBox Name="listBoxData" 
     DataContext="{Binding Source={StaticResource MainWindowViewModelDataSource}}" 
     SelectedItem="{Binding Path=SelectedBook, Mode=TwoWay}"
     ItemTemplate="{DynamicResource BookTemplate}"                              
     ItemsSource="{Binding Books}" />