The correct data binding to display the hierarchy

Question

Hi, everybody. I apologize a thousand times for my superficial and possibly trivial question, but I can't figure out how it works. What I need to get:
I need to display information about the Department and who it reports to in a hierarchical way in the app. What I did for this:
I Defined the class and implemented the interface:

 public class Departaments : INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;


        private string managementPositionName;


        private string whoReportsToTheDepartment;


        public string ManagementPositionName
        {
            get
            {
                return managementPositionName;
            }
            set
            {
                managementPositionName = value;
                PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(managementPositionName)));
            }
        }


        public string WhoReportsToTheDepartment
        {
            get
            {
                return whoReportsToTheDepartment;
            }
            set
            {
                whoReportsToTheDepartment = value;
                PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(WhoReportsToTheDepartment)));
            }
        }

       public Departaments(string formalManagePositionName, string formalWhoReportsToTheDepartment)
        {
            ManagementPositionName = formalManagePositionName;
            WhoReportsToTheDepartment = formalWhoReportsToTheDepartment;
        }
    }

Described the xaml markup:

<TreeView Grid.Row="1" Name="DepartamentHierarchy">
       <TreeViewItem Header="{Binding WhoReportsToTheDepartment}">
               <TreeViewItem Header="{Binding ManagementPositionName}"/>
        </TreeViewItem>
</TreeView>

Ideally, I need to create something similar to observablecollection. But all my attempts to link such a collection end in failure. The most I could do:

DataContext = new Departaments("3", "4");

As it is clear, only this line will be shown.

Answer 1

HI,
try following demo:

XAML:

<Window x:Class="WpfApp1.Window022"  
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"  
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"  
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"  
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"  
        xmlns:local="clr-namespace:WpfApp022"  
        mc:Ignorable="d"  
        Title="Window022" Height="450" Width="800">  
  <Window.DataContext>  
    <local:ViewModel/>  
  </Window.DataContext>  
  <Grid>  
    <TreeView ItemsSource="{Binding View}">  
      <TreeView.Resources>  
        <HierarchicalDataTemplate DataType="{x:Type local:Departament}"   
                                  ItemsSource="{Binding WhoReportsToTheDepartment}">  
            <TextBlock Text="{Binding Name}"/>  
        </HierarchicalDataTemplate>  
        <HierarchicalDataTemplate DataType="{x:Type local:Report}">  
          <TextBlock Text="{Binding ReportName}"/>  
        </HierarchicalDataTemplate>  
      </TreeView.Resources>  
    </TreeView>  
  </Grid>  
</Window>  

And code:

using System.Collections.ObjectModel;  
using System.ComponentModel;  
using System.Windows;  
using System.Windows.Data;  
  
namespace WpfApp022  
{  
  public class ViewModel  
  {  
    public ViewModel()  
    {  
      for (int i = 1; i < 10; i++)  
      {  
        Departament dp = new Departament() { Name = $"ManagementPosition {i}" };  
        col.Add(dp);  
        for (int k = 1; k < 5; k++) dp.WhoReportsToTheDepartment.Add(new Report() { ReportName = $"Report {k}" });  
      }  
      cvs.Source = col;  
    }  
  
    public ICollectionView View { get => cvs.View; }  
    private CollectionViewSource cvs = new CollectionViewSource();  
    private ObservableCollection<Departament> col = new ObservableCollection<Departament>();  
  }  
  
  public class Departament  
  {  
    public string Name { get; set; }  
    public ObservableCollection<Report> WhoReportsToTheDepartment { get; set; } = new ObservableCollection<Report>();  
  }  
  
  public class Report  
  {  
    public string ReportName { get; set; }  
  }  
}  

Result: