C# WPF manage treeview item templates

Question

Maybe this is quiet simple question but I have a problems with construction of a template for my treeview. I have some classes:

public class A //main class
{
    public B sth { get; set; }
    public C sthelse { get; set; }

    public A()
    {
        this.sth = new B(1000, "sth");
        this.sthelse = new C();
    }
}

public class B
{
    public D sth { get; set; }

    public B(ulong data, String abc)
    {
        this.sth = new D(data, abc);
    }
}

public class D
{
    public ulong data { get; private set; }
    public String abc { get; private set; }

    public D(ulong data, String abc)
    {
        this.data = data;
        this.abc = abc;
    }
}

And my question is how can I put it into treeview. I was testing HierarchicalDataTemplate but problem is that it have to be bound to collection. Any ideas how to create treeview like this:

• A
  • B
    • D
      • data
      • abc
  • C

Is it possible?

I am using this code:

<TreeView ItemsSource="{Binding}" ItemTemplate="{StaticResource phy}" />

<Window.Resources>
        <DataTemplate x:Key="d">
            <StackPanel Orientation="Vertical">
            <!-- Maybe there should be pairs property - value, maybe grid or whatever -->
                <TextBlock Text="{Binding Path=data}" />
                <TextBlock Text="{Binding Path=abc}" />
            </StackPanel>
        </DataTemplate>
        <HierarchicalDataTemplate x:Key="b" ItemsSource="{Binding Path=sth}" ItemTemplate="{StaticResource ResourceKey=d}">
                <TextBlock Text="D" />
        </HierarchicalDataTemplate>
        <!-- Cant bind also attribute C -->
        <HierarchicalDataTemplate x:Key="phy" ItemsSource="{Binding Path=sth}" ItemTemplate="{StaticResource ResourceKey=b}">
            <TextBlock Text="PHY" />                
        </HierarchicalDataTemplate>
</Window.Resources>

In code is:

public ObservableCollection<A> data { get; private set; }

And in constructor:

data = new ObservableCollection<A>();
treeView1.DataContext = data;
data.Add(new A());

Answer 1

ItemsSource property values must be IEnumerable. There's no way to avoid this. You can expose IEnumerables in a very simple way such as below, but I would recommend a better object model than this. You can take these classes and bind the ItemsSource properties of the tree and the HierarchicalDataTemplate to this new Nodes property.

public class A //main class
{
    public B sth { get; set; }
    public C sthelse { get; set; }

    public A()
    {
        this.sth = new B(1000, "sth");
        this.sthelse = new C();
    }

    public IEnumerable<object> Nodes
    {
        get
        {
            yield return B;
            yield return C;
        }
    }
}

public class B
{
    public D sth { get; set; }

    public B(ulong data, String abc)
    {
        this.sth = new D(data, abc);
    }

    public IEnumerable<object> Nodes
    {
        get
        {
            yield return D;
        }
    }
}

public class D
{
    public ulong data { get; private set; }
    public String abc { get; private set; }

    public D(ulong data, String abc)
    {
        this.data = data;
        this.abc = abc;
    }

    public IEnumerable<object> Nodes
    {
        get
        {
            yield return data;
            yield return abc;
        }
    }
}