当前文件： SmallBusinessStarterKit/smallbusiness_vb/App_Code/Catalog/Catalog.vb[2K，2009-6-12 11:54:22]，打开代码结构图

		            
 1Imports Microsoft.VisualBasic
 2Imports System
 3Imports System.Collections.Generic
 4Imports System.Configuration
 5Imports System.Web.Configuration
 6
 7'/<summary>
 8'/ class Catalog
 9'/ Provides static functions to access items & categories 
10'/ and serves as abastraction layer between the web Page and
11'/ actual data providers
12'/</summary>
13Public Class CatalogClass Catalog
14    Private Shared _isInitialized As Boolean = False
15    Private Shared _provider As CatalogProvider
16    Private Shared _providersSection As SmallBusinessDataProvidersSection
17
18    '/<summary>
19    '/ returns the current items data provider
20    '/</summary>    
21    Public Shared ReadOnly Property Provider()Property Provider() As CatalogProvider
22        Get
23            Initialize()
24            Return _provider
25        End Get
26    End Property
27
28
29    '<summary>
30    ' Returns item belonging to the category having id: 'parentCategoryId' 
31    '</summary>
32    Public Shared Function GetChildItems()Function GetChildItems(ByVal categoryId As String) As List(Of Item)
33
34        Return Provider.GetChildItems(categoryId)
35    End Function
36
37
38    '<summary>
39    ' Returns subcategories under the category having id: 'parentCategoryId'
40    '</summary>
41    Public Shared Function GetChildCategories()Function GetChildCategories(ByVal parentCategoryId As String) As List(Of Category)
42
43        Return Provider.GetChildCategories(parentCategoryId)
44    End Function
45
46
47    '<summary>
48    ' Returns an item matching the id
49    '</summary>
50    Public Shared Function GetItem()Function GetItem(ByVal itemId As String) As Item
51        Return Provider.GetItem(itemId)
52    End Function
53
54
55
56    '<summary>
57    'Initilizes a concrete data provider based on setting in web.config
58    'InvalidOperationException may be thrown if an actual provider cannot be instantiated
59    '</summary>
60    Private Shared Sub Initialize()Sub Initialize()
61        If Not _isInitialized Then
62            _providersSection = ConfigurationManager.GetSection("SmallBusinessDataProviders") '
63
64            If _providersSection Is Nothing Then
65                Throw New InvalidOperationException(Messages.ItemConfigNotFound)
66            End If
67            _provider = ProvidersHelper.InstantiateProvider(_providersSection.CatalogProviders(_providersSection.CatalogProviderName), GetType(CatalogProvider))
68
69            If _provider Is Nothing Then
70                Throw New InvalidOperationException(Messages.ItemProviderInstantiationError)
71            End If
72            _isInitialized = True
73        End If
74    End Sub 'Initialize
75End Class 'Catalog
76
77
78