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CH A PT E R 1 0 ■ L E A R N I N G A B O U T P E R S IS T E N CE 271
The IBinary2TextProcessor interface has a single method； Process（）； which has two param
eters： the binary stream and the text stream。 The implementation of IBinary2TextProcessor
would be responsible for reading the data from the binary stream and saving data to the
text stream。
The text…to…binary interface； IText2BinaryProcessor； follows a similar interface design；
except that the input and output stream types are reversed。
Imports System。IO
Public Interface IText2BinaryProcessor
Sub Process（ByVal input As TextReader； ByVal output As Stream）
End Interface
The idea of both interface declarations is to focus on transferring data from one stream
to another。
The shell for both data stream interfaces is very similar to the shell of the text…processing
stream； except that binary and text streams are involved。 The TextProcessor shell was respon
sible for knowing if the data stream was from the console or from a file。 When manipulating
binary streams； the source still needs to be ascertained； but instead of creating text streams；
binary streams are created。 If you understand the mechanics of using a text stream； you will
understand the mechanics of using a binary stream。
The following is the plete implementation of the text…to…binary bootstrap class。
Imports System。IO
Public Module Text2BinaryBootstrap
Public Sub DisplayHelp（）
Console。WriteLine（〃You need help？ Right now？〃）
End Sub
Public Sub Start（ByVal args As String（）； _
ByVal processor As IText2BinaryProcessor）
#If DEBUG_OUTPUT Then
Console。WriteLine（〃Argument count（〃 & args。Length & 〃）〃）
For Each argument As String In args
Console。WriteLine（〃Argument （〃 & argument & 〃）〃）
Next
#End If
Dim reader As TextReader = Nothing
Dim writer As Stream = Nothing
If args。Length = 0 Then
reader = Console。In
writer = Console。OpenStandardOutput（）
ElseIf args。Length = 1 Then
If args（0） = 〃…help〃 Then
Text2BinaryBootstrap。DisplayHelp（）
Return
End If
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272 CH AP T E R 1 0 ■ L E A R N I N G A B OU T P E R S IS TE N CE
reader = File。OpenText（args（0））
writer = Console。OpenStandardOutput（）
ElseIf args。Length = 2 Then
If args（0） 〃…out〃 Then
Text2BinaryBootstrap。DisplayHelp（）
Return
End If
reader = Console。In
writer = File。Open（args（1）； FileMode。Create）
ElseIf args。Length = 3 Then
If args（0） 〃…out〃 Then
Text2BinaryBootstrap。DisplayHelp（）
Return
End If
reader = File。OpenText（args（2））
writer = File。Open（args（1）； FileMode。Create）
Else
Text2BinaryBootstrap。DisplayHelp（）
Return
End If
processor。Process（reader； writer）
writer。Close（）
End Sub
End Module
The implementation is nearly identical to the Bootstrap class； the differences are bolded。
Notice that instead of using the predefined Console。Out data member； the OpenStandardOutput（）
method is called； and instead of File。CreateText（）； the File。Open（） method is called。
The implementation of the binary…to…text stream shell is nearly identical to the one for the
text…to…binary stream shell。 You can find it in this book’s downloadable source code。
Defining the Type
The central piece when converting from a text stream to a binary stream or vice versa is the
definition of a type。 The type might be a class or a struct； and it is identified as being a type that
can be read and written。 Identifying a type to be read and written is necessary so that when
reads or writes the type； the underlying infrastructure knows what to do。 Remember that
a binary data stream is a data stream where only the program knows what it means。 To help
read and write those types； you add identifiers that tell what to do。 Fortunately； you
don’t need to know the inner details of binary serialization； but just give an indication of
how to manage it。
For the lottery…prediction example； we will define a type that represents a lottery ticket。
The lottery ticket will contain the draw date； numbers； and bonus number。 Following is the
plete declaration （in the LottoLibrary project）。
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CH A PT E R 1 0 ■ L E A R N I N G A B O U T P E R S IS T E N CE 273
_
Public Class Ticket
Public Sub New（）
End Sub
Public Sub New（ByVal drawDate As DateTime； ByVal numbers As Integer（）； _
ByVal bonus As Integer）
_drawDate = drawDate
_numbers = numbers
_bonus = bonus
End Sub
Public Property Bonus（） As Integer
Get
Return _bonus
End Get
Set（ByVal value As Integer）
_bonus = value
End Set
End Property
Public Property DrawDate（） As DateTime
Get
Return _drawDate
End Get
Set（ByVal value As DateTime）
_drawDate = value
End Set
End Property
Public Property Numbers（） As Integer（）
Get
Return _numbers
End Get
Set（ByVal value As Integer（））
_numbers = value
End Set
End Property
Private _bonus As Integer
Private _drawDate As DateTime
Private _numbers As Integer（）
End Class
Ticket is plain…vanilla data class。 However； the bolded parts deserve an explanation。 The
first bolded part is a set of angled brackets surrounding the identifier Serializable； which
represents a attribute。 In ； you have the ability to describe types； methods； and so on。
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274 CH AP T E R 1 0 ■ L E A R N I N G A B OU T P E R S IS TE N CE
Attributes are descriptions that are used in a particular context。 As opposed to the identifiers
Public and MustInherit； which are descriptions that fundamentally describe how a type will
behave； the Serializable attribute describes the behavior of a type in a specific context—when
the object is to be converted from memory to a data stream and vice versa。 Fundamental descrip
tions are important to the runtime； whereas attributes are generally not important
to the runtime； but important to libraries that the runtime will execute。
■Note Serialization is the process of turning an object into a format that can be saved or sent over the
network。 Deserialization is the process of retrieving the serialized object。
The Serializable attribute describes the ability to serialize the type as it is declared。 When
Ticket is converted into a binary stream； the programmer does not nee