Imports System.Runtime.InteropServices

<StructLayout(LayoutKind.Sequential)> _
Public Structure WSAData
Dim wVersion As Short
Dim wHighVersion As Short
<MarshalAs(UnmanagedType.ByValTStr, SizeConst:=WSADESCRIPTION_LEN + 1)> _
Dim szDescription As Char
Dim szSystemStatus As String
Dim iMaxSockets As UInt16
Dim iMaxUdpDg As UInt16
Dim lpVendorInfo As Int32
End Structure

Error message "type MarshalAs is not defined"

really don't know how to do it~~... can anyone help me on this?