Passing structure as argument through files/functions - vb.net

Question

I can't get to pass structure as argument through subs/functions in different files of single vbnet project like I use to in earlier MS basic versions.
Here is short example of situation:
Module1.vb
Imports System.IO
Structure mymultitry
Dim index As Integer
<VBFixedString(6)> Dim name As String
Dim weight As Double
End Structure
Module Module1
Public mysetupfile = "mysetup.dat"
Public Sub rwfile(ByVal rw As Integer, ByVal myrecord As Integer, ByVal mmt As mymultitry)
'EDIT: Thanks to SteveDog - proper line should be:
'Public Sub rwfile(ByVal rw As Integer, ByVal myrecord As Integer, ByRef mmt As mymultitry)
Dim fnum As Integer
fnum = FreeFile()
FileOpen(fnum, mysetupfile, OpenMode.Random, OpenAccess.ReadWrite, OpenShare.Shared, Len(mmt))
If rw Then
FilePut(fnum, mmt, myrecord)
Else
FileGet(fnum, mmt, myrecord)
End If
FileClose(fnum)
End Sub
End Module
Form1.vb
Public Class Form1
Dim mmt As mymultitry
Dim mmt1 As mymultitry
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
With mmt
.index = 4
.name = "Helga"
.weight = 128.1445
End With
rwfile(1, 1, mmt) 'write
rwfile(0, 1, mmt1) 'read
'all zero here !?!
Debug.Print(mmt1.index)
Debug.Print(mmt1.name)
Debug.Print(mmt1.weight)
End Sub
End Class
File "mysetup.dat" is reachable and data is saved correctly what I can see with HxD.
But read part seem's to not work as expected.
Please any help on reliable passing structure as argument without too much public elements based on upper example.

Answer 1

I strongly suggest you rewrite your code to use the new .NET IO methods in the System.IO.File class, but, that aside, I think your problem with your existing code is that you need to change your mmt argument from ByVal to ByRef.