Reading a file error in VB.NET?

The way this file works, there is an empty buffer, then the checksum is the user then the byte, which gives the user the count of the name of the letter, then the byte for how many bytes to go to the next user and the byte for which the user file, the user saves their settings.

the usersm loop in the IF statement sets the entire file stream to be retrieved. However, almost exactly the same code Disclaimers still specifically str.Read (xnl, 0, USN - 1) in the code still seems that reading the very beginning of the file, despite the position of FileStream being set earlier, does anyone know What is happening here?

it's in vb2005

Private Sub readusersdata(ByVal userdatafile As String)
    ListView1.BeginUpdate()
    ListView1.Items.Clear()
    Using snxl As IO.Stream = IO.File.Open(userdatafile, IO.FileMode.Open)

        Using str As New IO.StreamReader(snxl)
            str.BaseStream.Position = 4
            Dim usersm As Integer = str.BaseStream.ReadByte()
            Dim users As Integer = usersm
            While users > 0
                If usersm = users Then
                    Dim trailtouser As Integer = 0
                    str.BaseStream.Position = 6
                    Dim ust As Integer = str.BaseStream.ReadByte()
                    str.BaseStream.Position = 8
                    Dim snb(ust - 1) As Char
                    str.ReadBlock(snb, 0, ust)
                    Dim bst = New String(snb)
                    If usersm = 1 Then
                        str.BaseStream.Position = 16
                    Else
                        str.BaseStream.Position = 15
                    End If
                    cLVN(ListView1, bst, str.BaseStream.ReadByte)
                    str.BaseStream.Position = 8 + snb.Length
                    str.BaseStream.Position += str.BaseStream.ReadByte + 1
                Else

                    Dim usn As Integer = str.BaseStream.ReadByte
                    str.BaseStream.Position += 2
                    Dim chrpos As Integer = str.BaseStream.Position
                    Dim xnl(usn - 1) As Char
                    str.Read(xnl, 0, usn - 1)
                    Dim skpbyte As Integer = str.BaseStream.ReadByte
                    str.BaseStream.Position += 3
                    Dim udata As Integer = str.BaseStream.ReadByte


                End If

                users -= 1

            End While
        End Using
    End Using
    ListView1.EndUpdate()
End Sub