views:

553

answers:

2

Greetings,

I'm using WPF with a Model-View-ViewModel pattern, and I have a view model with an IsSelected property which I want to bind to a TreeViewItem's IsSelected property for all TreeViewItems in the scope. I'm attempting to do this with a Style and a Setter. This works apparently for the root-level TreeViewItems, but not for their children. Why is this? How can I have this apply to all TreeViewItem controls?

Here is the view XAML:

<UserControl x:Class="MyApp.AllAreasView"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             xmlns:MyApp="clr-namespace:MyApp"
             mc:Ignorable="d" 
             d:DesignHeight="300" d:DesignWidth="700">
<UserControl.Resources>
    <Style TargetType="{x:Type TreeViewItem}">
        <Setter Property="IsSelected"
                Value="{Binding IsSelected, Mode=TwoWay}"/>
    </Style>

    <MyApp:CountVisibilityConverter x:Key="CountVisibilityConverter" />

    <HierarchicalDataTemplate x:Key="AreaTemplate"
                              DataType="AreaViewModel"
                              ItemsSource="{Binding Path=SubareasCollectionView}">
        <WrapPanel>
            <TextBlock Text="{Binding Path=Name}" Margin="0 0 8 0" />
            <TextBlock DataContext="{Binding Path=Subareas}" 
                       Text="{Binding Path=Count, StringFormat= (\{0\})}"
                       Visibility="{Binding Path=Count, Converter={StaticResource CountVisibilityConverter}}" />
        </WrapPanel>
    </HierarchicalDataTemplate>
</UserControl.Resources>

<TreeView ItemsSource="{Binding TopLevelAreas}"
          ItemTemplate="{StaticResource AreaTemplate}">
</TreeView>

</UserControl>
+1  A: 

I think we'll need more info to answer your question. Specifically, what your view model(s) look like. Below is an example you can copy and paste that works fine.

Window1.xaml:

<Window x:Class="WpfApplication1.Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="clr-namespace:WpfApplication1"
    Title="Window1" Height="300" Width="300">
    <Window.Resources>
        <Style TargetType="{x:Type TreeViewItem}">
            <Setter Property="Background" Value="{Binding Background}"/>
        </Style>

        <HierarchicalDataTemplate x:Key="ItemTemplate" DataType="local:DataItem" ItemsSource="{Binding Path=Children}">
            <TextBlock Text="{Binding Name}" />
        </HierarchicalDataTemplate>
    </Window.Resources>

    <TreeView ItemsSource="{Binding}" ItemTemplate="{StaticResource ItemTemplate}"/>
</Window>

Window1.xaml.cs:

using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Windows;
using System.Windows.Media;

namespace WpfApplication1
{
    public partial class Window1 : Window
    {
        public Window1()
        {
            InitializeComponent();

            var dis = new ObservableCollection<DataItem>();
            var di = new DataItem() { Name = "Top", Background = Brushes.Red };
            di.Children.Add(new DataItem() { Name = "Second", Background = Brushes.Blue });

            dis.Add(di);
            DataContext = dis;
        }
    }

    public class DataItem
    {
        public DataItem()
        {
            Children = new ObservableCollection<DataItem>();
        }

        public string Name
        {
            get;
            set;
        }

        public ICollection<DataItem> Children
        {
            get;
            set;
        }

        public Brush Background
        {
            get;
            set;
        }
    }
}

HTH,
Kent

Kent Boogaart
Thanks for the working example (and inferring the simple view model). It turns out that I had been generating two separate sets of view models and the PropertyChanged event wasn't being handled correctly on my view models since I had hooked one, and WPF the other. Following the trail of the event and examining the results of GetInvocationList() of the PropertyChanged delegate lead me to find this. Since you proved it works, I'll accept this as the answer.
codekaizen
A: 

working with view models you will get very friendly with the ItemContainerStyle property. what you were doing in your code set the data template for the root level. what you want to do is style each of the items in the treeview, which you can do like so.

<TreeView ItemsSource="{Binding TopLevelAreas}"
          ItemContainerStyle="{StaticResource AreaTemplate}">
</TreeView>

enjoy

Aran Mulholland