Question

I am trying the absolute simplest use of HierarchicalDataTemplate to bind nested data to a WPF TreeView. For some reason, the children of my tree are not visible:

                                               

Here is the entire 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:src="clr-namespace:WpfApplication1"
        Title="MainWindow" Height="350" Width="525">
    <TreeView Name="ctTree">
        <TreeView.Resources>
            <HierarchicalDataTemplate DataType = "{x:Type src:MyClass}"
                                      ItemsSource = "{Binding Path=Children}">
                <TextBlock Text="{Binding Path=Name}"/>
            </HierarchicalDataTemplate>
        </TreeView.Resources>
    </TreeView>
</Window>

and here’s all of C# behind this, apart from usings and the namespace:

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

        var collection = new ObservableCollection<MyClass>
        {
            new MyClass { Name = "parent one" },
            new MyClass { Name = "parent two" },
        };
        collection[0].Children.Add(new MyClass { Name = "child one" });
        collection[0].Children.Add(new MyClass { Name = "child two" });
        ctTree.ItemsSource = collection;
    }
}

class MyClass
{
    public string Name { get; set; }
    public ObservableCollection<MyClass> Children
        = new ObservableCollection<MyClass>();
}

Note that the data template does actually apply to the items: the data is taken from the Name property, and if the template didn’t apply would show as “MyClass” instead.

How do I get the children to show? I seem to be doing exactly the same thing as all examples on HierarchicalDataTemplate.

Answer 1

MyClass.Children is a field, not a property. You cannot bind to a field, convert Children field to a property and everything should work then:

class MyClass
{
    public string Name { get; set; }
    public ObservableCollection<MyClass> Children { get; private set; }

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