Example for WPF Treeview data binding

Question

I'm beginner for C# and WPF.

When I tried to figure out how to bind data to treeview, I find a example in Microsoft learn, the link is https://learn.microsoft.com/en-us/dotnet/api/system.windows.hierarchicaldatatemplate?view=windowsdesktop-7.0.

It is a pity in this example only XAML code is provided, for objects there is only description but not code. Please see the picture below for the objects description.

I code the objects with my limited C# knowledge, as below.

Objects: ListLeagueList

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Collections.ObjectModel;

namespace Treeview01
{
    public class ListLeagueList : ObservableCollection<League>
    {
        public ListLeagueList() : base()
        {
            Add(new League("League A"));
            Add(new League("League B"));
            Add(new League("League C"));
        }
    }
}

Objects: League

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Collections.ObjectModel;

namespace Treeview01
{
    public class League
    {
        public string Name { get; set; }

        List<Division> Divisions  = new List<Division>();
        public League(string name) //: base()
        {
            Name = name;
            Divisions.Add(new Division("DivisionA"));
            Divisions.Add(new Division("DivisionB"));
            Divisions.Add(new Division("DivisionC"));
        }
        private League()
        {
        }
    }
}

Objects: Division

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Collections.ObjectModel;

namespace Treeview01
{
    public class Division
    {
        public string Name { get; set; }

        List<Team> Teams = new List<Team>();
        public Division(string name) //: base()
        {
            Name = name;
            Teams.Add(new Team("Bear"));
            Teams.Add(new Team("Rocket"));
        }
        private Division()
        {
        }

    }
}

Objects: Team

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Treeview01
{
    public class Team
    {
        public string Name { get; set; }

        public Team(string name)
        {
            Name = name;
        }

        private Team()
        {
        }
    }
}

XAML:

<Window x:Class="Treeview01.Window1"
      xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
      Title="HierarchicalDataTemplate Sample"
      xmlns:src="clr-namespace:Treeview01">
        <DockPanel>
            <DockPanel.Resources>
                <src:ListLeagueList x:Key="MyList"/>
    
                <HierarchicalDataTemplate DataType    = "{x:Type src:League}"
                                    ItemsSource = "{Binding Path=Divisions}">
                    <TextBlock Text="{Binding Path=Name}"/>
                </HierarchicalDataTemplate>
    
                <HierarchicalDataTemplate DataType    = "{x:Type src:Division}"
                                    ItemsSource = "{Binding Path=Teams}">
                    <TextBlock Text="{Binding Path=Name}"/>
                </HierarchicalDataTemplate>
    
                <DataTemplate DataType="{x:Type src:Team}">
                    <TextBlock Text="{Binding Path=Name}"/>
                </DataTemplate>
                
            </DockPanel.Resources>
    
            <Menu Name="menu1" DockPanel.Dock="Top" Margin="10,10,10,10">
                <MenuItem Header="My Soccer Leagues"
                      ItemsSource="{Binding Source={StaticResource MyList}}" />
            </Menu>
    
            <TreeView>
                <TreeViewItem ItemsSource="{Binding Source={StaticResource MyList}}" Header="My Soccer Leagues" />
            </TreeView>
    
        </DockPanel>
    </Window>

XAML.CS:

using System.Windows;

namespace Treeview01
{
    /// <summary>
    /// Interaction logic for Window1.xaml
    /// </summary>
    public partial class Window1 : Window
    {
        public Window1()
        {
            InitializeComponent();
        }

    }
}

With the code above, only the first level data is represented, as the picture below.

Please check and correct my code.

Answer 1

Divisions and Teams can not be recognized in Xaml, because they are not public properties.

Devisions

public List<Division> Divisions { set; get; } = new List<Division>();

Teams

public List<Team> Teams { set; get; } = new List<Team>();