[VB6, Vista+] Host Windows Explorer on your form: navigation tree and/or folder

[fafalone]

IExplorerBrowser

IExplorerBrowser is an easy to use, more complete version of IShellView (in fact, it has an IShellView at its core that you can access) that lets you have a complete Explorer frame on your form, with very little code. You can either have just a plain file view, or with a navigation tree and toolbar. It uses all the same settings and does all the same things as Explorer, and your program can interact with those actions to do things like browse for files, or be the basis of a namespace extension.
The only complication is that there's no event notifying of an individual file selection within the view, and getting a list of selected files is fairly complex- however there is a function to do it in the demo project.
Here's how it looks if you're just using folder view without the frames:

INamespaceTreeControl

If all you want is the navigation tree, you have the INamespaceTreeControl. It's got a decent amount of options for however you want to display things, including checkboxes. There is a wide range of events that you're notified of via the event sink, and most of these use IShellItem- the demo project does show to to convert that into a path, but it's a very useful interface to learn if you're going to be doing shell programming. The selection is reported through IShellItemArray, which is slightly easier than IDataObject.
It's got one little quirk though... you have the option to set the folder icons yourself, but if you don't want to do that and just use the default icon that you see in Explorer, you have to return -1, which requires a v-table swap. The demo project shows how to go both ways, no thanks to MSDN and their complete lack of documentation of this.
But this is by far the easiest to create way of having a full-featured Explorer-like navigation- I've made a regular TreeView into this, and it took hundreds of lines and heavy subclassing. This is a simple object. (Note that it does support some advanced features through related interfaces, like custom draw, drop handling, and accessibility... these interfaces are included in oleexp, but have not been brought to the sample project here, perhaps in the future I'll do a more in-depth one if there's any interest)

Requirements
Windows Vista or higher required as these interfaces did not exist in earlier OS versions
oleexp.tlb: Modern Interfaces Type Library v4.0 or higher (17 Jun 2015) - Only required in the IDE.
mIID.bas - oleexp add-on module, included in the oleexp download

These 'controls' create themselves- all you need is a blank form, and here's the creation code for a basic idea of how these things work (code to initialize some variables omitted):

Set pNST = New NamespaceTreeControl
pNST.Initialize Me.hWnd, prc, lFlag
Set pAdv = New cNSTEvents
Set pUnkAdv = pAdv
pNST.TreeAdvise pUnkAdv, lpck
pNST.InsertRoot 0, isiDesk, SHCONTF_FOLDERS, NSTCRS_EXPANDED Or NSTCRS_VISIBLE, pif

UPDATE: Enumerating selection in virtual location for IExplorerBrowser.
So I was showing how this demo can be used to browse FTP sites and realized the IDataObject/DragQueryFile method of obtaining the selection fails in virtual folders that don't have local paths. This is an alternative method that will get their IShellItems, display names, and (if applicable and including network) paths, so that you can further interact with them (for instance, to copy to/from FTP, you can pass the IShellItems to IFileOperation even if there's no valid path):

'frmBasic

Private Sub Command1_Click()
Dim hr As Long
Dim sOut As String
Dim pIDO As oleexp.IDataObject
Dim psv As IShellView
Dim fmt As FORMATETC
Dim stg As STGMEDIUM
Dim hDrop As Long
Dim uNumFiles As Long
Dim i As Long
Dim Filename As String

pEBrowse.GetCurrentView IID_IShellView, psv
If (psv Is Nothing) Then
    Debug.Print "Failed to created IShellView"
    Exit Sub
End If

Dim psia As IShellItemArray
Dim penm As IEnumShellItems
Dim lpName As Long
Dim psiChild As IShellItem

psv.GetItemObject SVGIO_SELECTION, IID_IShellItemArray, psia
If (psia Is Nothing) = False Then
    psia.EnumItems penm
    If (penm Is Nothing) = False Then
        Do While (penm.Next(1&, psiChild, i) = NOERROR)
            psiChild.GetDisplayName SIGDN_NORMALDISPLAY, lpName
            Filename = BStrFromLPWStr(lpName)
            sOut = sOut & "Display: " & Filename
            psiChild.GetDisplayName SIGDN_DESKTOPABSOLUTEPARSING, lpName
            Filename = BStrFromLPWStr(lpName)
            sOut = sOut & " | AbsParse=" & Filename & vbCrLf
        Loop
    Else
        Debug.Print "Failed to enumerate selection."
    End If
Else
    Debug.Print "Failed to get selection array."
End If

'old way that only works on non-virtual locations:        
'psv.GetItemObject SVGIO_SELECTION, IID_IDataObject, pIDO
'If (pIDO Is Nothing) Then
'    Debug.Print "Failed to create IDataObject"
'    Exit Sub
'End If
'
'
'fmt.cfFormat = CF_HDROP
'fmt.dwAspect = DVASPECT_CONTENT
'fmt.lindex = -1
'fmt.TYMED = TYMED_HGLOBAL
'stg.TYMED = TYMED_HGLOBAL
'
'hr = pIDO.GetData(fmt, stg)
'Debug.Print "GetData hr=" & hr
'
'hDrop = GlobalLock(stg.Data)
'
'uNumFiles = DragQueryFile(hDrop, &HFFFFFFFF, "", 0)
'Debug.Print "got nfiles=" & uNumFiles
'For i = 0 To (uNumFiles - 1)
'    Filename = String$(260, 0)
'    Call DragQueryFile(hDrop, i, Filename, Len(Filename))
'    If (InStr(Filename, vbNullChar)) > 1 Then
'        Filename = Left$(Filename, InStr(Filename, vbNullChar) - 1)
'        Debug.Print "filename=" & Filename
'        sOut = sOut & Filename & ", "
'    End If
'Next i
'Call GlobalUnlock(stg.Data)
'ReleaseStgMedium VarPtr(stg)
Debug.Print "output=" & sOut
Text1.Text = sOut
End Sub

It's basically the same way it's done on the INamespaceTreeControl form, only difference being that you still need to go through IShellView.

UPDATE: Showing a Custom List of Files
(8/2018) This project allows you to browse to any particular location on the system, but what if you want to do something like display a Search Results folder, or some other view where all the files reside in different locations? There's an interface that allows you to easily do just that. See the new project:
[VB6] Display search results or other custom file set in IExplorerBrowser