Binaryworld - GetClassesByInterface - Retrieve all the classes that implement a give ... [ VB -> COM-COM+ ]

' Return all classes of the type library specified in
' TypeLibFile parameter that support a certain interface.
' the interface can be specified as an Object or through its IID

' Be sure that "TypeLib Information" type library (TlbInf32.tlb)
' is referenced in your VB project.

Function GetClassesByInterface(ByVal TypeLibFile As String, _
  ObjectOrInterfaceIID As Variant) As Collection
  Dim TLI As New TLIApplication
  Dim TypeLibrary As TypeLibInfo
  Dim Class As CoClassInfo
  Dim Interface As InterfaceInfo
  Dim IID_objInterface As String

  ' prepare the result
  Set GetClassesByInterface = New Collection

  ' raises an error if unable to open the type library
  ' (e.g. file not found or not a TLB)
  Set TypeLibrary = TLI.TypeLibInfoFromFile(TypeLibFile)

  ' get the IID of requested interface
  If VarType(ObjectOrInterfaceIID) = vbString Then
    IID_objInterface = ObjectOrInterfaceIID
  Else
    IID_objInterface = TLI.InterfaceInfoFromObject(ObjectOrInterfaceIID) _
      .Guid
  End If

  ' fill the return collection with names of
  ' classes that implement the interface
  For Each Class In TypeLibrary.CoClasses
    For Each Interface In Class.Interfaces
      ' compare GUIDs
      If StrComp(Interface.Guid, IID_objInterface, vbTextCompare) = 0 Then
        ' ok, this class implements the interface
        GetClassesByInterface.Add Class.Name, Class.Name
        Exit For
      End If
    Next
  Next

End Function