Private Function StringToBytearray(ByVal str As String) As Byte()
 
        Dim buffersize As Integer = str.Length * 2
        Dim bytearray(buffersize - 1) As Byte
        Dim Handle As IntPtr
        Try
            Handle = Marshal.StringToBSTR(str)
            Marshal.Copy(Handle, bytearray, 0, buffersize)
        Finally
            Marshal.FreeBSTR(Handle)
        End Try
 
        Return bytearray
    End Function

  Dim test As String = ""
  For i As Integer = 0 To UShort.MaxValue
      test &= ChrW(i)   
  Next i
 
 
  Dim byt As Byte() = StringToBytearray(test)
 
  'Check
  For i As Integer = 0 To byt.Length - 1 Step 2
      Dim bt() As Byte = BitConverter.GetBytes(AscW(test(i \ 2)))
      If byt(i) <> bt(0) Then Stop
      If byt(i + 1) <> bt(1) Then Stop
  Next i