[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
struct WLAN_AVAILABLE_NETWORK_LIST
    {
        internal   uint dwNumberOfItems;
        internal   uint dwIndex;
        internal   WLAN_AVAILABLE_NETWORK[] wlanAvailableNetwork;

    internal WLAN_AVAILABLE_NETWORK_LIST(IntPtr ppAvailableNetworkList)
        {
            dwNumberOfItems = (uint)Marshal.ReadInt32(ppAvailableNetworkList);
            dwIndex = (uint)Marshal.ReadInt32(ppAvailableNetworkList, 4);
            wlanAvailableNetwork = new WLAN_AVAILABLE_NETWORK[dwNumberOfItems];

            for (int i = 0; i < dwNumberOfItems; i++)
            {
               IntPtr pWlanAvailableNetwork = new IntPtr(ppAvailableNetworkList.ToInt32() + i * Marshal.SizeOf(typeof(WLAN_AVAILABLE_NETWORK)) + 8);
                wlanAvailableNetwork[i] = (WLAN_AVAILABLE_NETWORK)Marshal.PtrToStructure(pWlanAvailableNetwork, typeof(WLAN_AVAILABLE_NETWORK));
            }
         }
    }

VB Definition:

<StructLayout(LayoutKind.Sequential, CharSet := CharSet.Unicode)> _

Friend Structure WLAN_AVAILABLE_NETWORK_LIST

            Friend dwNumberOfItems As UInteger
            Friend dwIndex As UInteger
            Friend wlanAvailableNetwork() As WLAN_AVAILABLE_NETWORK

        Friend Sub New(ByVal ppAvailableNetworkList As IntPtr)
                dwNumberOfItems = CUInt(Marshal.ReadInt32(ppAvailableNetworkList))
                    dwIndex = CUInt(Marshal.ReadInt32(ppAvailableNetworkList, 4))
                    wlanAvailableNetwork = New WLAN_AVAILABLE_NETWORK(dwNumberOfItems - 1){}

                    For i As Integer = 0 To dwNumberOfItems - 1
                       Dim pWlanAvailableNetwork As New IntPtr(ppAvailableNetworkList.ToInt32() + i * Marshal.SizeOf(GetType(WLAN_AVAILABLE_NETWORK)) + 8)
                        wlanAvailableNetwork(i) = CType(Marshal.PtrToStructure(pWlanAvailableNetwork, GetType(WLAN_AVAILABLE_NETWORK)), WLAN_AVAILABLE_NETWORK)
                    Next i
        End Sub

End Structure