选择TreeView项时如何显示ListBox项

Question

So I have a task of building a mail application for school. I am having a problem with one of the parts.

I have a TreeView and a ListBox . TreeView has few items in it (Inbox, trash, draft). Now what I am trying to do, is that when I select and TreeView item certain ListBox Items will appear in the ListBox . (purpose of the ListBox is to show the mails in that "folder").

I have been looking into this, and there are some suggestions with ListAray and DataBinding , but I am very new and have no idea how to implement any of those.

What I have at this poit is:

<TreeView Grid.Row="2" Grid.ColumnSpan="1" VerticalAlignment="Stretch" HorizontalAlignment="Left" Margin="10,10,0,10"  Name="treeView1" Width="100" FontSize="14" SelectedItemChanged="treeView1_SelectedItemChanged">
    <TreeViewItem Header="Prejeto" IsSelected="True">
        <TreeViewItem Header="Prebrano" />
        <TreeViewItem Header="Neprebrano" />
    </TreeViewItem>

    <TreeViewItem Header="Poslano" />
    <TreeViewItem Header="Osnutki" />
    <TreeViewItem Header="Izbrisano" />
    <TreeViewItem Header="Nezaželeno" />
    <TreeViewItem />
</TreeView>

XAML ListBox :

<ListBox Name="seznamSporocil" Grid.Column="1" Grid.Row="2"  HorizontalAlignment="Left" Margin="10,10,0,10"  VerticalAlignment="Stretch" Width="100" FontWeight="Bold" FontFamily="Arial" MouseDoubleClick="seznamSporocil_MouseDoubleClick" />

SelectedItemChanged :

private void treeView1_SelectedItemChanged(object sender, RoutedPropertyChangedEventArgs<object> e)
{

}

Answer 1

When working with WPF, data binding is your best friend. Just bind ItemsSource of list box with some collection property of tree view's selected item.

Update .

Here's the complete sample (just create WPF Application project). Model:

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

    public ObservableCollection<MailItem> Items
    {
        get
        {
            return items ?? (items = new ObservableCollection<MailItem>());
        }
    }
    private ObservableCollection<MailItem> items;

    public ObservableCollection<MailFolder> SubFolders
    {
        get
        {
            return subFolders ?? (subFolders = new ObservableCollection<MailFolder>());
        }
    }
    private ObservableCollection<MailFolder> subFolders;
}

public class MailItem
{
    public string Subject { get; set; }
}

XAML:

<Window x:Class="WpfApplication1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:local="clr-namespace:WpfApplication1"
        Title="MainWindow" Height="350" Width="525">
    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition />
            <ColumnDefinition />
        </Grid.ColumnDefinitions>

        <TreeView x:Name="MailTreeView" ItemsSource="{Binding}">
            <TreeView.Resources>
                <HierarchicalDataTemplate DataType="{x:Type local:MailFolder}" ItemsSource="{Binding SubFolders}">
                    <TextBlock Text="{Binding Name}"/>
                </HierarchicalDataTemplate>
            </TreeView.Resources>
        </TreeView>

        <ListBox Grid.Column="1" ItemsSource="{Binding Path=SelectedItem.Items, ElementName=MailTreeView}">
            <ListBox.ItemTemplate>
                <DataTemplate DataType="{x:Type local:MailItem}">
                    <TextBlock Text="{Binding Subject}"/>
                </DataTemplate>
            </ListBox.ItemTemplate>
        </ListBox>
    </Grid>
</Window>

And this is data context setup:

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();

        DataContext = new[] 
        {
            new MailFolder
            {
                Name = "Prejeto",
                SubFolders = 
                {
                    new MailFolder
                    {
                        Name = "Prebrano",
                        Items = 
                        {
                            new MailItem { Subject = "A" },
                            new MailItem { Subject = "B" },
                            new MailItem { Subject = "C" },
                        }
                    },
                    new MailFolder
                    {
                        Name = "Neprebrano",
                        Items = 
                        {
                            new MailItem { Subject = "D" },
                            new MailItem { Subject = "E" },
                        }
                    },
                },
                Items = 
                {
                    new MailItem { Subject = "M" },
                    new MailItem { Subject = "N" },
                }
            },
            new MailFolder
            {
                Name = "Poslano",
                Items = 
                {
                    new MailItem { Subject = "F" },
                    new MailItem { Subject = "G" },
                }
            },
            new MailFolder
            {
                Name = "Osnutki",
                Items = 
                {
                    new MailItem { Subject = "H" },
                }
            },
            new MailFolder
            {
                Name = "Izbrisano",
                Items = 
                {
                    new MailItem { Subject = "I" },
                    new MailItem { Subject = "J" },
                    new MailItem { Subject = "K" },
                }
            },
            new MailFolder
            {
                Name = "Nezaželeno",
                Items = 
                {
                    new MailItem { Subject = "L" },
                }
            }
        };
    }
}

Note, that if you want to reflect changes, made to properties of your model classes, you need to implement INotifyPropertyChanged interface.