Treeview items don't expand - wpf

Question

I'm developing a WPF application for my company, and everything needs to look the same way corresponding to our company's look. Therefore I have to make a custom folder explorer, which will feature a treeview of the current directory.
In order to make it easier, I've made the following class, which is basically a TreeViewItem that stores a DirectoryInfo and automaticely browses subfolders when expanded (not to browse everything at once and make the software faster). Here is my code :
Private Class TreeViewPlus
Inherits TreeViewItem
Public dir As IO.DirectoryInfo
Public Sub New()
End Sub
Public Sub New(dir As DirectoryInfo)
Me.dir = dir
Try
If Not dir.EnumerateDirectories Is Nothing Then 'If there are subdirectories, I add an empty item to enable the expansion
Me.Items.Add(New TreeViewPlus)
End If
Catch ex As Exception
End Try
End Sub
Private Sub TreeViewPlus_Expanded(sender As Object, e As RoutedEventArgs) Handles Me.Expanded
Me.Items.Clear()
Try
For Each folder In dir.EnumerateDirectories()
Dim item As TreeViewPlus = New TreeViewPlus(folder)
item.Name = Text.RegularExpressions.Regex.Replace(folder.FullName, "[^a-zA-Z0-9]", "")
item.Header = folder.Name
Me.Items.Add(item)
Next
Catch ex As Exception
End Try
End Sub
End Class
And here is the code where I initialize the first directories: (TRV_Arbre is the name of my TreeView)
Sub New()
...
For Each Drive As IO.DriveInfo In IO.DriveInfo.GetDrives
Dim item As TreeViewPlus = New TreeViewPlus(Drive.RootDirectory)
item.Header = Drive.Name
TRV_Arbre.Items.Add(item)
Next
...
End Sub
The Issue I've got is that the first level of items correctly expand, but not the following ones.
See here : https://youtu.be/E6BJbKal5Sk
I've already debugged my code a little, and it correctly creates the different Items.
Can anyone help me for this ? Thanks in advance.

Answer 1

There is a simple way to solve this problem and that is to Override the OnExpanded Sub on the Base TreeViewItem class instead of implementing your own Expanded method. Then in the end you execute MyBase.OnExpanded(e) method which seems to contain the correct update events to send out to whomever listens. In this case your TreeView.
Protected Overrides Sub OnExpanded(e As RoutedEventArgs)
Me.Items.Clear()
Try
For Each folder In dir.EnumerateDirectories()
Dim item As TreeViewPlus = New TreeViewPlus(folder)
item.Name = Text.RegularExpressions.Regex.Replace(folder.FullName, "[^a-zA-Z0-9]", "")
item.Header = folder.Name
Me.Items.Add(item)
Next
Catch ex As Exception
End Try
MyBase.OnExpanded(e)
End Sub