Display all drives, files, and subfolders in treeview - vb.net

Question

I'm looking for the simplest way to display all drives, files, and subfolders in a treeview. If someone's got a snippet of code to do this that they don't mind sharing I would really appreciate it.
The closest I've gotten was this code I tried using, but it gave me a "IOException was unhandled" error saying "The device is not ready." error at runtime (after about 5-10 sec) on the line below
Dim folders() As String = IO.Directory.GetDirectories(dir)
underneath is the rest of the code
Private Sub Main_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Dim drives As System.Collections.ObjectModel.ReadOnlyCollection(Of IO.DriveInfo) = My.Computer.FileSystem.Drives
Dim rootDir As String = String.Empty
For i As Integer = 0 To drives.Count - 1
rootDir = drives(i).Name
TreeView1.Nodes.Add(rootDir)
PopulateTreeView(rootDir, TreeView1.Nodes(i))
Next
End Sub
Private Sub PopulateTreeView(ByVal dir As String, ByVal parentNode As TreeNode)
Dim folder As String = String.Empty
Try
Dim folders() As String = IO.Directory.GetDirectories(dir)
If folders.Length <> 0 Then
Dim childNode As TreeNode = Nothing
For Each folder In folders
childNode = New TreeNode(folder)
parentNode.Nodes.Add(childNode)
PopulateTreeView(folder, childNode)
Next
End If
Catch ex As UnauthorizedAccessException
parentNode.Nodes.Add(folder & ": Access Denied")
End Try
End Sub

Answer 1

Seems like you're off to a good start. The IOException you receive is most likely caused by your procedure trying to list contents on an empty disc drive, which is obviously impossible.
The fix is simple:
For i As Integer = 0 To drives.Count - 1
If Not drives(i).IsReady Then
Continue For
End If
rootDir = drives(i).Name
TreeView1.Nodes.Add(rootDir)
PopulateTreeView(rootDir, TreeView1.Nodes(i))
Next
Besides that, I recommend not loading folder contents until a node is clicked. Limit the recursive call to 1 level (current directory + content of all its subdirectories). That way, you get the best performance while still being able to determine whether a subdirectory should have the treeview expand button.