Question

I have:

public class Extra
{
public string Name {get;set;}
}

and I have

public class CarViewModel
{
 public ObservableCollection<Extra> OwningExtras { get; set; }
public static IEnumerable<Extra> AllExtras
        {
            get
            {
                return Extra.GetAllExtras();
            }
        }
public CarViewModel()
{
owningExtras=Extra.GetAvailableExtrasForCar(idCar)
}
}

and CarView looks like:

   <Grid >

        <ListBox ItemsSource="{Binding}" Name="lbExtras">
            <ListBox.ItemTemplate>
                <DataTemplate>
                    <StackPanel Orientation="Horizontal">
                        <CheckBox"/> //How implement adding and removing Extras
                        <TextBlock Text="{Binding Path=Name}" />
            </StackPanel>
                </DataTemplate>
            </ListBox.ItemTemplate>
        </ListBox>

    </Grid>
</UserControl>

And I wonder what connect to this.DataContext? And then how to notice that something is changed (Checked checkbox means that this car has this extra)

Answer 1

Below code will display all items in the collection AllExtras in the listbox and fill collection CheckedExtras with items that are checked. This is only one of many ways to solve this. Not sure what you meant with “how to notice that something is changed”. Do you need to get notified that collection with checked items is updated? In that case you can use an ObservableCollection instead and listen its CollectionChanged event.

XAML:

<Window x:Class="ListBoxTest.Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Height="300" Width="300">
    <StackPanel>

        <ListBox ItemsSource="{Binding Path=AllExtras}">
            <ListBox.ItemTemplate>
                <DataTemplate>
                    <StackPanel Orientation="Horizontal">
                        <CheckBox Click="OnCheckBoxClick" /> 
                        <TextBlock Text="{Binding Path=Name}" />
                    </StackPanel>
                </DataTemplate>
            </ListBox.ItemTemplate>
        </ListBox>

    </StackPanel>

</Window>

Code behind:

using System.Collections.Generic;
using System.Windows;
using System.Windows.Controls;

namespace ListBoxTest
{
    public partial class Window1 : Window
    {
        public Window1()
        {
            InitializeComponent();

            DataContext = new VM();
        }

        private void OnCheckBoxClick(object sender, RoutedEventArgs e)
        {
            VM vm = DataContext as VM;
            CheckBox checkBox = sender as CheckBox;
            Extra extra = checkBox.DataContext as Extra;
            if (checkBox.IsChecked.GetValueOrDefault())
            {
                vm.CheckedExtras.Add(extra);
            }
            else
            {
                vm.CheckedExtras.Remove(extra);
            }
        }
    }

    public class VM
    {
        public VM()
        {
            CheckedExtras = new List<Extra>();
            AllExtras = new List<Extra>() { new Extra() { Name = "A" }, new Extra() { Name = "B" }, new Extra() { Name = "C" }, };
        }

        public List<Extra> CheckedExtras { get; private set; }
        public List<Extra> AllExtras { get; private set; }
    }

    public class Extra
    {
        public string Name { get; set; }
    } 
}