Public MustInherit Class TransactionForm
  Inherits System.Windows.Forms.Form

  Public Sub New()
    MyBase.New()

    'This call is required by the Windows Form Designer.
    InitializeComponent()
  End Sub

  Public Function Save(ByVal FileName As String) As Boolean
    'declare a file and serialize class
    Dim TranFile As Stream
    Dim BinSerialize As BinaryFormatter

    'Set the return value to True
    Save = True

    'Use Try/Catch to handle any errors
    Try
      'Allocate and create a new file and serialize objects
      TranFile = File.Open(FileName, FileMode.Create)
      BinSerialize = New BinaryFormatter()

      'Serialize the form data
      BinSerialize.Serialize(TranFile, AmountField.ToString())
      BinSerialize.Serialize(TranFile, MemoField.ToString())
      BinSerialize.Serialize(TranFile, DateField.ToString())

      'Call SaveData() to save derived class's data
      SaveData(BinSerialize, TranFile)
    Catch
      'Indicate an error occurred
      Save = False
    End Try

    TranFile.Close()
  End Function

  'Declare Abstract method to save derived class's data
  Protected MustOverride Sub SaveData(ByRef BinSerialize _
            As BinaryFormatter, ByRef TranFile As Stream)

   ...
End Class