Exercise 109 in Visual Basic .NET

Making QR Code JIS X 0510 in Visual Basic .NET Exercise 109
Exercise 109
QR Code Generator In VB.NET
Using Barcode maker for Visual Studio .NET Control to generate, create QR Code ISO/IEC18004 image in VS .NET applications.
In almost every case, the structural patterns described result in code that has a more complex structure than you might have used to do the same job Why is this and what advantage do the structural patterns bring to software (you may be able to think of several)
Printing Bar Code In Visual Basic .NET
Using Barcode creator for Visual Studio .NET Control to generate, create bar code image in .NET applications.
1053 Behavioural Patterns
QR-Code Creation In C#.NET
Using Barcode generation for Visual Studio .NET Control to generate, create QR Code image in VS .NET applications.
So far, we have examined patterns that provide for the exible creation of objects and optimization of software structures Behavioural patterns are about the generalization of algorithms and the assignment of responsibilities among objects The behavioural patterns codify how objects communicate with each other in a way that can assist our understanding of control ow in a program Instead of managing control ow, you deal with object inter-connections; this in turn manages control ow Behavioural patterns are the most diverse group This is probably because the history of computing has concentrated more on algorithms than on structures Structure is a feature that supports good algorithms, but algorithms make the data work
Paint Quick Response Code In VS .NET
Using Barcode encoder for ASP.NET Control to generate, create QR Code image in ASP.NET applications.
10531 The Observer Pattern
QR Printer In Visual Studio .NET
Using Barcode drawer for Visual Studio .NET Control to generate, create QR Code image in .NET applications.
This is also known as Subject-Observer, since it allows us to de ne the interaction between an object (the subject) and another object that is interested in its state (the observer) The purpose is to set up an automatic interaction between subject and observer so that updates need not be performed by the application code Visual Basic is particularly suited to the pattern because a number of the built-in user-interface controls are potential subjects or observers
Create Bar Code In Visual Basic .NET
Using Barcode creator for .NET Control to generate, create barcode image in .NET framework applications.
105 Software Patterns
Barcode Drawer In VB.NET
Using Barcode printer for .NET framework Control to generate, create bar code image in .NET framework applications.
Assume, for example, that we wish to make sure that all of the controls that are currently displaying state information about a speci c object are kept up to date We might, for example, have displayed two or more forms, each of which displays speci c properties of an object, and these forms might also allow us to edit the object The Observer pattern allows us to keep the two or more observer forms in synch with the current state of the object by providing a Notify() method The subject class keeps a list of all of its current observers, and dispatches the Notify() message to each whenever its state changes The end result is an automatic update of all observers, without any need to code the updates into the application program For example, a simple Subject class is shown in Listing 1019
Code 3/9 Creator In Visual Basic .NET
Using Barcode generation for .NET Control to generate, create Code 39 Extended image in .NET framework applications.
Public Class Subject Private mvarWidth As Integer Private mvarHeight As Integer Private mvarGraphicFile As String Private mvarObservers As ArrayList
Create Code 128C In VB.NET
Using Barcode encoder for Visual Studio .NET Control to generate, create Code 128 Code Set C image in Visual Studio .NET applications.
'Width of an image 'Height of an image 'Picture file name 'The list of observers
Data Matrix 2d Barcode Maker In Visual Basic .NET
Using Barcode generation for VS .NET Control to generate, create ECC200 image in VS .NET applications.
Public Sub New(ByVal W As Integer, ByVal H As Integer, _ ByVal F As String) 'Set up the sizes and picture file mvarWidth = W mvarHeight = H mvarGraphicFile = F 'And create the observer collection mvarObservers = New ArrayList() End Sub Public Property Width() As Integer Get Return mvarWidth End Get Set(ByVal Value As Integer) mvarWidth = Value Update() 'Update Width in all observers End Set End Property Public Property Height() As Integer Get Return mvarHeight End Get Set(ByVal Value As Integer) mvarHeight = Value Update() 'Update Height in all observers End Set End Property Public Property GraphicFile() As String Get Return mvarGraphicFile End Get
Bar Code Drawer In Visual C#
Using Barcode printer for .NET Control to generate, create barcode image in .NET applications.
10 n Object Modelling
Generating Bar Code In VS .NET
Using Barcode maker for ASP.NET Control to generate, create bar code image in ASP.NET applications.
Set(ByVal Value As String) mvarGraphicFile = Value Update() 'Update file in all observers End Set End Property Public Sub AddObserver(ByVal Obs As ObserverForm) 'Add a new observer to the list mvarObserversAdd(Obs) 'Update it ObsNotify(Me) End Sub Private Sub Update() 'Update all observers Dim Obs As ObserverForm For Each Obs In mvarObservers ObsNotify(Me) Next End Sub Public Sub Dispose() 'Object is going, so destroy all its observers Dim Obs As Form For Each Obs In mvarObservers ObsDispose() Next End Sub End Class Listing 1019: A Subject class part of the Subject-Observer pattern
Scanning USS Code 128 In VS .NET
Using Barcode recognizer for .NET Control to read, scan read, scan image in Visual Studio .NET applications.
With the Subject class able to maintain a list of observers (in this case forms, but an Observer object does not need to be visible), we can now turn to the creation of Observer objects The only pattern requirement for these is that they must implement a Notify() method and have some way of accessing the subject s state With that in mind, it is a good idea to create an abstract base Observer class that we can use to de ne the Notify() method protocol (see Listing 1020)
Encode Code 128B In .NET
Using Barcode creation for ASP.NET Control to generate, create ANSI/AIM Code 128 image in ASP.NET applications.
Public Class ObserverForm Inherits SystemWindowsFormsForm + Windows Form Designer Generated Code Public Overridable Sub Notify(ByVal S As Subject) 'Base class declares the Notify method 'Sub-classes must define how they behave End Sub End Class Listing 1020: An Observer base class a form
Decoding UPC-A In Visual Studio .NET
Using Barcode reader for VS .NET Control to read, scan read, scan image in .NET applications.
UPCA Generation In .NET
Using Barcode maker for ASP.NET Control to generate, create UCC - 12 image in ASP.NET applications.
Bar Code Recognizer In .NET Framework
Using Barcode decoder for Visual Studio .NET Control to read, scan read, scan image in .NET applications.
Printing Data Matrix ECC200 In .NET Framework
Using Barcode maker for ASP.NET Control to generate, create Data Matrix 2d barcode image in ASP.NET applications.