Business Object Creation in VB.NET

Printing PDF-417 2d barcode in VB.NET Business Object Creation

Business Object Creation
Generating PDF 417 In Visual Basic .NET
Using Barcode generator for VS .NET Control to generate, create PDF 417 image in .NET applications.
www.OnBarcode.com
Scanning PDF-417 2d Barcode In VB.NET
Using Barcode recognizer for VS .NET Control to read, scan read, scan image in VS .NET applications.
www.OnBarcode.com
First, it s important to recognize that the key classes in the framework are those that business developers will use as they create business objects, but that these are a small subset of what s available. In fact, many of the framework classes are never used directly by business developers. Figure 2-10 shows only those classes the business developer will typically use.
Barcode Generation In Visual Basic .NET
Using Barcode printer for Visual Studio .NET Control to generate, create Barcode image in VS .NET applications.
www.OnBarcode.com
DataMatrix Maker In Visual Basic .NET
Using Barcode encoder for VS .NET Control to generate, create Data Matrix 2d barcode image in .NET applications.
www.OnBarcode.com
Figure 2-10. Framework classes used directly by business developers
Make EAN / UCC - 13 In Visual Basic .NET
Using Barcode generation for .NET framework Control to generate, create EAN-13 Supplement 5 image in .NET framework applications.
www.OnBarcode.com
Creating Code 39 In Visual Basic .NET
Using Barcode drawer for .NET framework Control to generate, create Code39 image in Visual Studio .NET applications.
www.OnBarcode.com
Obviously, the business developer may periodically interact with other classes as well, but these are the ones that will be at the center of most activity. Classes or methods that the business developer shouldn t have access to will be scoped to prevent accidental use. Table 2-1 summarizes each class and its intended purpose.
Barcode Creator In VB.NET
Using Barcode encoder for Visual Studio .NET Control to generate, create Barcode image in Visual Studio .NET applications.
www.OnBarcode.com
Generating Leitcode In Visual Basic .NET
Using Barcode generator for VS .NET Control to generate, create Leitcode image in .NET applications.
www.OnBarcode.com
CHAPTER 2 s FRAMEWORK DESIGN
Making PDF 417 In C#
Using Barcode encoder for VS .NET Control to generate, create PDF 417 image in .NET framework applications.
www.OnBarcode.com
PDF417 Encoder In .NET Framework
Using Barcode encoder for ASP.NET Control to generate, create PDF-417 2d barcode image in ASP.NET applications.
www.OnBarcode.com
Table 2-1. Business Framework Base Classes
Code128 Creation In Java
Using Barcode drawer for Java Control to generate, create Code128 image in Java applications.
www.OnBarcode.com
Encoding Universal Product Code Version A In Java
Using Barcode drawer for Eclipse BIRT Control to generate, create UCC - 12 image in BIRT reports applications.
www.OnBarcode.com
Class
QR Code Generation In Java
Using Barcode drawer for Android Control to generate, create Denso QR Bar Code image in Android applications.
www.OnBarcode.com
Print Barcode In Java
Using Barcode printer for Java Control to generate, create Barcode image in Java applications.
www.OnBarcode.com
BusinessBase(Of T) BusinessListBase(Of T, C) CommandBase
USS-128 Maker In None
Using Barcode drawer for Software Control to generate, create GTIN - 128 image in Software applications.
www.OnBarcode.com
Draw UPC - 13 In Java
Using Barcode maker for Java Control to generate, create EAN 13 image in Java applications.
www.OnBarcode.com
Purpose
Generate PDF417 In VS .NET
Using Barcode generation for ASP.NET Control to generate, create PDF-417 2d barcode image in ASP.NET applications.
www.OnBarcode.com
Draw UPC A In None
Using Barcode encoder for Font Control to generate, create UPC-A Supplement 5 image in Font applications.
www.OnBarcode.com
Inherit from this class to create a single editable business object such as Customer, Order, or OrderLineItem. Inherit from this class to create an editable collection of business objects such as PaymentTerms or OrderLineItems. Inherit from this class to implement a command that should run on the application server, such as implementation of a Customer.Exists or an Order.ShipOrder command. Inherit from this class to create a single read-only business object such as OrderInfo or ProductStatus. Inherit from this class to create a read-only collection of objects such as CustomerList or OrderList. Inherit from this class to create a read-only collection of key/value pairs (typically for populating drop-down list controls) such as PaymentTermsCodes or CustomerCategories.
PDF417 Scanner In C#
Using Barcode scanner for VS .NET Control to read, scan read, scan image in Visual Studio .NET applications.
www.OnBarcode.com
QR-Code Scanner In Visual Studio .NET
Using Barcode reader for .NET framework Control to read, scan read, scan image in .NET applications.
www.OnBarcode.com
ReadOnlyBase(Of T) ReadOnlyListBase(Of T, C) NameValueListBase(Of K, V)
Let s discuss each class in a bit more detail.
BusinessBase
The BusinessBase class is the base from which all editable (read-write) business objects will be created. In other words, to create a business object, inherit from BusinessBase, as shown here: <Serializable()> _ Public Class Customer Inherits BusinessBase(Of Customer) End Class When creating a subclass, the business developer must provide the specific type of new business object as a type parameter to BusinessBase(Of T). This allows the generic BusinessBase type to expose strongly typed methods corresponding to the specific business object type. Behind the scenes, BusinessBase(Of T) inherits from Csla.Core.BusinessBase, which implements the majority of the framework functionality to support editable objects. The primary reason for pulling the functionality out of the generic class into a normal class is to enable polymorphism. Polymorphism is what allows you to treat all subclasses of a type as though they were an instance of the base class. For instance, all Windows Forms Form1, Form2, and so forth can all be treated as type Form. You can write code like this: Dim form As Form = New Form2 form.Show() This is polymorphic behavior, in which the variable form is of type Form, but references an object of type Form2. The same code would work with Form1, because both inherit from the base type Form. It turns out that generic types are not polymorphic like normal types. Another reason for inheriting from a non-generic base class is to make it simpler to customize the framework. If needed, you can create alternative editable base classes starting with the functionality in Core.BusinessBase. Csla.Core.BusinessBase and the classes from which it inherits provide all the functionality discussed earlier in this chapter, including n-level undo, tracking of broken rules, dirty tracking, object persistence, and so forth. It supports the creation of root (top-level) objects and child
CHAPTER 2 s FRAMEWORK DESIGN
objects. Root objects are objects that can be retrieved directly from and updated or deleted within the database. Child objects can only be retrieved or updated in the context of their parent object.
s Note
Throughout this book, it is assumed that you are building business applications, in which case almost all objects are ultimately stored in the database at one time or another. Even if an object isn t persisted to a database, you can still use BusinessBase to gain access to the n-level undo, validation rule tracking, and dirty tracking features built into the framework.
For example, an Invoice is typically a root object, though the LineItem objects contained by an Invoice object are child objects. It makes perfect sense to retrieve or update an Invoice, but it makes no sense to create, retrieve, or update a LineItem without having an associated Invoice. To make this distinction, BusinessBase includes a method that can be called to indicate that the object is a child object: MarkAsChild(). By default, business objects are assumed to be root objects, unless this method is invoked. This means that a child object might look like this: <Serializable()> Public Class Child Inherits BusinessBase(Of Child) Private Sub New() MarkAsChild() End Sub End Class The BusinessBase class provides default implementations of the data access methods that exist on all root business objects. These methods will be called by the data portal mechanism. These default implementations all raise an error if they re called. The intention is that the business objects can opt to override these methods if they need to support, create, fetch, insert, update, or delete operations. The names of these methods are as follows: DataPortal_Create() DataPortal_Fetch() DataPortal_Insert() DataPortal_Update() DataPortal_DeleteSelf() DataPortal_Delete() Though Overridable implementations of these methods are in the base class, developers will typically implement strongly typed versions of DataPortal_Create(), DataPortal_Fetch(), and DataPortal_Delete(), as they all accept a criteria object as a parameter. The Overridable methods declare this parameter as type Object, of course; but a business object will typically want to use the actual data type of the criteria object itself. This is discussed in more detail in s 7 and 8. The data portal also supports three other (optional) methods for pre- and post-processing and exception handling. The names of these methods are as follows: DataPortal_OnDataPortalInvoke() DataPortal_OnDataPortalInvokeComplete() DataPortal_OnDataPortalException()
Copyright © OnBarcode.com . All rights reserved.