public static extern int GetIpAddrTable(IntPtr pIpAddrTable, ref int pdwSize, bool bOrder);

GetIpAddrTable Lib "iphlpapi.dll" (ByRef ipTable As IntPtr, ByRef tableSize As IntPtr, ByVal ordered As Boolean) As UInt32

[DllImport(S"IPHLPAPI.DLL", EntryPoint=S"GetIpAddrTable", SetLastError=true, CharSet=CharSet::Unicode, ExactSpelling=true)]

GetIpAddrTable( IntPtr.Zero, ref nBufSize, false );

int r = GetIpAddrTable( pBuf, ref nBufSize, false );