Question

I have a custom class that I would like to bind a WPF TreeView that has three tiers. Each tier needs to be bound like this:

    Monitor 
     --> LCD
          --> Samsung 1445 LCD
     --> CRT
          --> Sony 125 CRT

Here is the example code:

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
        SystemInventory sysInventory = new SystemInventory();
        //Possibly do something like this.
        _myTreeView.DataContext = sysInventory.DeviceGroupInstances; 
    }

    public class SystemInventory
    {
        public ObservableCollection<DeviceGroup> DeviceGroupInstances { get; set; }

        public SystemInventory()
        {
            DeviceGroupInstances = new ObservableCollection<DeviceGroup>();
            DeviceGroupInstances.Add(new DeviceGroup("Monitor"));
        }
    }

    public class DeviceGroup
    {
        public string DeviceGroupName { get; set; }
        public ObservableCollection<DeviceType> DeviceTypeInstances { get; set; }

        public DeviceGroup(string deviceGroupName)
        {
            DeviceTypeInstances = new ObservableCollection<DeviceType>();
            DeviceGroupName = deviceGroupName;

            if (deviceGroupName == "Monitor")
            {
                DeviceTypeInstances.Add(new DeviceType("LCD"));
                DeviceTypeInstances.Add(new DeviceType("CRT"));
            }               
        }
    }

    public class DeviceType
    {
        public string DeviceTypeName { get; set; }
        public ObservableCollection<DeviceInstance> DeviceInstances { get; set; }

        public DeviceType(string deviceGroupName)
        {
            DeviceInstances = new ObservableCollection<DeviceInstance>();
            DeviceTypeName = deviceGroupName;

            if (deviceGroupName == "Monitor")
            {
                DeviceInstances.Add(new DeviceInstance("Samsung 1445 LCD"));
            }
            else
            {
                DeviceInstances.Add(new DeviceInstance("Sony 125 CRT"));
            }                
        }
    }

    public class DeviceInstance
    {
        public string DeviceInstanceName { get; set; }

        public DeviceInstance(string instanceName)
        {
            DeviceInstanceName = instanceName;
        }
    }
}

Answer 1

First FIX

Change CTOR:

public MainWindow()
    {
        InitializeComponent();
        SystemInventory sysInventory = new SystemInventory();
        //Possibly do something like this.
        this.Content = sysInventory;
    }

Second FIX

Use XAML below (add to MainWindow), where {x:Type pc:MainWindow+SystemInventory} used for nested classes

<Window.Resources>
    <DataTemplate DataType="{x:Type pc:MainWindow+SystemInventory}">
        <TreeView ItemsSource="{Binding DeviceGroupInstances}"/>
    </DataTemplate>

    <HierarchicalDataTemplate DataType="{x:Type pc:MainWindow+DeviceGroup}" ItemsSource="{Binding DeviceTypeInstances}">
        <Label Content="{Binding DeviceGroupName}"/>
    </HierarchicalDataTemplate>

    <HierarchicalDataTemplate DataType="{x:Type pc:MainWindow+DeviceType}" ItemsSource="{Binding DeviceInstances}">
        <Label Content="{Binding DeviceTypeName}"/>
    </HierarchicalDataTemplate>

    <DataTemplate DataType="{x:Type pc:MainWindow+DeviceInstance}">
        <Label Content="{Binding DeviceInstanceName}"/>
    </DataTemplate>

</Window.Resources>

---

About namespaces

Namespace is what you need to know to use classes. If your classes have namespace:

namespace MyCompany.MyProject.MyComponent
{
   public class SystemInventory
   {
      ....
   }
}

This namespace should be added to XAML with alias to use:

<Window x:Class="MyCompany.MyProject.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

    xmlns:myAlias="clr-namespace:MyCompany.MyProject.MyComponent" 

    Title="Window1" Height="300" Width="350">
    <Window.Resources>
    ...

Now you can use this classes in XAML like:

<DataTemplate DataType="{x:Type myAlias:DeviceInstance}">
   <Label Content="{Binding DeviceInstanceName}"/>
</DataTemplate>