WPF TreeView HierarchicalDataTemplate get TreeViewItem

Question

I am using a HierarchicalDataTemplate to bind my classes to a TreeView with checkboxes. I have the code working fine and everything is displayed fine, but I'd like to be able to get a list of children of an item in my treeview.

When a checkbox is clicked, I want to be able to select the parent nodes and child nodes. If I had access to the TreeViewItem that is supposed to wrap the checkbox then I could easily do this, but the Parent property of the Checkbox is null... I can only seem to gain access to my classes that are mapped in the HierarchicalDataTemplate.

<TreeView Margin="12" Name="trv1" SelectedItemChanged="trv1_SelectedItemChanged">
        <TreeView.Resources>
            <HierarchicalDataTemplate DataType="{x:Type src:Location}" ItemsSource="{Binding Path=Sublocations}">
                <CheckBox Content="{Binding Name}" Tag="{Binding}" IsChecked="{Binding IsChecked}" Click="checkBox_Click"/>
            </HierarchicalDataTemplate>

            <HierarchicalDataTemplate DataType="{x:Type src:Sublocation}" ItemsSource="{Binding Path=Children}">
                <CheckBox Content="{Binding Name}" Tag="{Binding}" IsChecked="{Binding IsChecked}" Click="checkBox_Click"/>
            </HierarchicalDataTemplate>

            <DataTemplate DataType="{x:Type src:Child}">
                <CheckBox Content="{Binding Name}" Tag="{Binding}" IsChecked="{Binding IsChecked}" Click="checkBox_Click"/>
            </DataTemplate>

        </TreeView.Resources>
    <TreeView.ItemContainerStyle>
        <Style TargetType="TreeViewItem">
            <Setter Property="IsSelected" Value="{Binding IsChecked}"/>
        </Style>
    </TreeView.ItemContainerStyle>
</TreeView>

Answer 1

You need to add Children and Parent node in your TreeViewItem classes. You need to set Parent/Children on initialization.

<HierarchicalDataTemplate x:Key="TreeViewItem" ItemsSource="{Binding Children}">
    <CheckBox Margin="2" IsChecked="{Binding IsChecked, Mode=TwoWay}" Content="{Binding Name}" />
</HierarchicalDataTemplate>
<TreeView ItemsSource="{Binding Countries}" ItemTemplate="{StaticResource TreeViewItem}" />

In your viewModels.

public class MainPageViewModel
{
    public ObservableCollection<Country> Countries {get;set;}
}

public class Country
{
    public string Name {get; set;}
    public bool IsChecked {get;set;}
    public IEnumerable<State> Children {get; set;}
    // Do not need parent for this.
}

public class State
{
    public string Name {get; set;}
    public bool IsChecked {get; set;}
    public Country Parent {get; set;}
    public IEnumerable<City> Children {get; set;}
}

public class City
{
    public string Name {get; set;}
    public bool IsChecked {get; set;} 
    public State Parent {get; set;}
}