Structure Artikel
     Dim Mc As String
     Dim Num As Integer
     Dim Bez As String
     Dim Vki As Integer
     Dim AnzVol As Integer
     Dim AnzLer As Integer
End Structure

Public Sub SatzZerlegen(SatzGelesen As String)
 
       Dim myArtikel As New Artikel
 
       'Zuerst die Textfelder
       myArtikel.Mc = Mid(SatzGelesen, 1, 10)
       myArtikel.Bez = Mid(SatzGelesen, 15, 10)
 
End Sub

       ...
       myArtikel.vki = CInt(Mid(SatzGelesen, 26, 4))

  Structure Artikel
    Dim Mc As String '10 Byte
    Dim Num As Short '2 Byte
    Dim Bez As String '10 Byte
    Dim Vki As Integer '4 Byte
    Dim AnzVol As Integer '4 Byte
    Dim AnzLer As Integer '4 Byte
  End Structure
 
  Sub LeseDatei()
    Dim s = IO.File.OpenRead("Datei")
    Dim r = New IO.BinaryReader(s)
 
    'einen Satz lesen
    Dim a As New Artikel
    a.Mc = r.ReadChars(10)
    a.Num = BcdToInt16(r.ReadInt16)
    a.Bez = r.ReadChars(10)
    a.Vki = r.ReadInt32
    a.AnzVol = r.ReadInt32
    a.AnzLer = r.ReadInt32
 
    r.Close()
  End Sub
 
  'Binärcodierte Dezimalzahl, in Binärzahl umwandeln
  Function BcdToInt16(w As Short) As Short
    Dim rg As Short = 0
    For i = 0 To 3
      rg += ((w >> i * 4) And &HFS) * CShort(10 ^ i)
    Next
    Return rg
  End Function

Zitat:

Da VB.net keine String-Variablen mit fester Länge kennt...

EALA FREYA FRESENA

    Function BcdToInt32(w As Integer) As Integer
        Dim rg As Integer = 0
        For i = 0 To 7
            rg += ((w >> i * 4) And &HFS) * CInt(10 ^ i)
        Next
        Return rg
    End Function

  Function BcdToInt16(b() As Byte) As Short
    Array.Reverse(b)
    Dim w = BitConverter.ToInt16(b, 0)
    Dim rg As Short = 0
    For i = 0 To 3
      rg += ((w >> i * 4) And &HFS) * CShort(10 ^ i)
    Next
    Return rg
  End Function
 
  a.Num = BcdToInt16(r.ReadBytes(2))

  Function BcdToInt32(b() As Byte) As Integer
    Array.Reverse(b)
    Dim w = BitConverter.ToInt32(b, 0)
    Dim rg As Integer = 0
    For i = 0 To 7
      rg += ((w >> i * 4) And &HF) * CInt(10 ^ i)
    Next
    Return rg
  End Function
 
  a.Num = BcdToInt32(r.ReadBytes(4))