FileOpen i VB.NET

Structure Person
  <VBFixedString(30)> Dim Name As String
  Dim ID As Integer
End Structure

FileOpen(1, "TESTFILE", OpenMode.Output, OpenAccess.Write, , 34)
Dim ttt As Person
ttt.Name = "test"
Print(1, ttt)
FileClose(1)

Når jeg køre ovenstående, giver PRINT kommandoen fejlen:
File I/O with type 'Person' is not valid.
Hvad gør jeg galt ????