Friend Declare Function EnumWindows Lib "user32.dll" (ByVal lpEnumFunc As EnumWindowsProc, ByVal lParam As Int32) As Int32

Example:

''' <summary>Gets all the top-level windows</summary>
        ''' <returns>List of all top-level windows</returns>
        ''' <exception cref="API.Win32APIException">An error occured</exception>
        Public Shared ReadOnly Property TopLevelWindows() As IReadOnlyList(Of Win32Window)
            Get
                Dim List As New List(Of Win32Window)
                If API.EnumWindows(New API.EnumWindowsProc(Function(hWnd As Integer, lParam As Integer) AddToList(List, New Win32Window(hWnd))), 0) Then
                    Return New ReadOnlyListAdapter(Of Win32Window)(List)
                Else
                    Dim ex As New API.Win32APIException
                    If ex.NativeErrorCode <> 0 Then
                        Throw ex
                    Else
                        Return New ReadOnlyListAdapter(Of Win32Window)(List)
                    End If
                End If
            End Get
        End Property
	''' <summary>Adds <paramref name="item"/> to <paramref name="List"/> and returns true</summary>
        ''' <param name="List"><see cref="List(Of T)"/> to add item to</param>
        ''' <param name="item">Item to be added</param>
        ''' <typeparam name="T">Type of <paramref name="item"/></typeparam>
        ''' <returns>True</returns>
        Private Shared Function AddToList(Of T)(ByVal List As List(Of T), ByVal item As T) As Boolean
            List.Add(item)
            Return True
        End Function