supercontentrotator.vb

asp.net技术内幕的书配源码

Imports System
Imports System.Web.UI
Imports System.Web.UI.WebControls
Imports System.Collections
Imports System.Data

Namespace Superexpert


'*********************************************************************
'
' SuperContentRotator Class
'
' The SuperContentRotator enables you to randomly display a list of
' content items from a data source. This control supports templates
' through its ItemTemplate property.
'
' See the SuperContentRotator.aspx file for
' samples of using this control.
'
' This control is from the book ASP.NET Unleashed written by 
' Stephhen Walther and published by SAMS publishing.
'
'*********************************************************************

Public Class SuperContentRotator
    Inherits WebControl
    Implements INamingContainer 
    
    Private _items As New ArrayList()
    Private _dataTextField As String = String.Empty
    Private _dataValueField As String = String.Empty
    Private _contentFile As String = String.Empty
    Private _dataSource As Object
    Private _dataMember As String
    Private _repeatLayout As RepeatLayout = RepeatLayout.Table
    Private _itemTemplate As ITemplate = Nothing
    
    
    Private _tableStyle As New TableStyle()
    Private _itemStyle As New TableItemStyle()
    Private _alternatingItemStyle As New TableItemStyle()
    
    
    
    '*********************************************************************
    '
    ' ItemCount Property
    '
    ' Represents the number of items from the data source.
    '
    '*********************************************************************
    
    Public Property ItemCount() As Integer
        Get
            If ViewState("ItemCount") Is Nothing Then
                Return 0
            Else
                Return ViewState("ItemCount")
            End If
        End Get 
        Set
            ViewState("ItemCount") = value
        End Set
    End Property 
    
    
    '*********************************************************************
    '
    ' RepeatItems Property
    '
    ' Represents the number of items to display from the data source.
    '
    '*********************************************************************
    
    Public Property RepeatItems() As Integer
        Get
            If ViewState("RepeatItems") Is Nothing Then
                Return 1
            Else
                Return ViewState("RepeatItems")
            End If
        End Get 
        Set
            ViewState("RepeatItems") = value
        End Set
    End Property 
    
    
    '*********************************************************************
    '
    ' RepeatLayout Property
    '
    ' Represents whether content items are displayed in an HTML table.
    '
    '*********************************************************************
    
    Public Property RepeatLayout() As RepeatLayout
        Get
            Return _repeatLayout
        End Get
        Set
            _repeatLayout = value
        End Set
    End Property 
    
    
    '*********************************************************************
    '
    ' DataSource Property
    '
    ' The source of the content items. Either this property or 
    ' the ContentFile property must be set.
    '
    '*********************************************************************
    
    Public Property DataSource() As Object
        Get
            Return _dataSource
        End Get
        Set
            _dataSource = value
        End Set
    End Property 
    
    '*********************************************************************
    '
    ' DataMember Property
    '
    ' The name of the DataTable when a DataSet is supplied for the
    ' data source.
    '
    '*********************************************************************
    
    Public Property DataMember() As String
        Get
            Return _dataMember
        End Get
        Set
            _dataMember = value
        End Set
    End Property 
    
    
    '*********************************************************************
    '
    ' ContentFile Property
    '
    ' The virtual path to an XML file that contains content items.
    '
    '*********************************************************************
    
    Public Property ContentFile() As String
        Get
            Return _contentFile
        End Get
        Set
            _contentFile = value
        End Set
    End Property 
    
    
    '*********************************************************************
    '
    ' TableStyle Property
    '
    ' Formats the table displayed around the content items.
    '
    '*********************************************************************
    
    Public ReadOnly Property TableStyle() As TableStyle
        Get
            Return _tableStyle
        End Get
    End Property 
    
    
    '*********************************************************************
    '
    ' ItemStyle Property
    '
    ' Formats each content item.
    '
    '*********************************************************************
    
    Public ReadOnly Property ItemStyle() As TableItemStyle
        Get
            Return _itemStyle
        End Get
    End Property 
    
    
    
    '*********************************************************************
    '
    ' AlternatingItemStyle Property
    '
    ' Formats every other content item.
    '
    '*********************************************************************
    
    Public ReadOnly Property AlternatingItemStyle() As TableItemStyle
        Get
            Return _alternatingItemStyle
        End Get
    End Property
     
    
    
    
    '*********************************************************************
    '
    ' GetDataSource Method
    '
    ' Calculate the data source.
    '
    '*********************************************************************
    Private Function GetDataSource(dataSource As Object, dataMember As String) As IEnumerable
        If TypeOf dataSource Is IEnumerable Then
            Return CType(dataSource, IEnumerable)
        End If 
        Dim dst As DataSet = dataSource '
        'ToDo: Error processing original source shown below
        '            
        '            DataSet dst = dataSource as DataSet; 
        '--------------------------------------^--- Syntax error: ';' expected
        If Not (dst Is Nothing) Then
            If dataMember <> String.Empty Then
                Return dst.Tables(DataMember).DefaultView
            Else
                Return dst.Tables(0).DefaultView
            End If
        Else
            Throw New ArgumentException("Invalid data source!")
        End If
    End Function 'GetDataSource
     
    
    
    
    '*********************************************************************
    '
    ' GetDataSourceFromFile Method
    '
    ' Retrieve a DataSet that represents an XML file.
    '
    '*********************************************************************
    Private Function GetDataSourceFromFile(fileName As String) As IEnumerable
        Dim dst As New DataSet()
        dst.ReadXml(Page.MapPath(fileName))
        Return dst.Tables(0).DefaultView
    End Function 'GetDataSourceFromFile
    
    
    '*********************************************************************
    '
    ' ItemTemplate Property
    '
    ' Represents the ItemTemplate.
    '
    '*********************************************************************
    
    <TemplateContainer(GetType(ContentItem))>  _
    Public Property ItemTemplate() As ITemplate
        Get
            Return _itemTemplate
        End Get
        Set
            _itemTemplate = value
        End Set
    End Property
     
    
    '*********************************************************************
    '
    ' OnDataBinding Method
    '
    ' When databind is called, create the control hiearchy from the
    ' datasource.
    '
    '*********************************************************************
    Protected Overrides Sub OnDataBinding(e As EventArgs)
        ' Use an enumerator to creates the items collection
        Dim objData As IEnumerable = Nothing
        If _contentFile <> String.Empty Then
            objData = GetDataSourceFromFile(_contentFile)
        Else
            objData = GetDataSource(_dataSource, _dataMember)
        End If 
        Dim objEnum As IEnumerator = objData.GetEnumerator()
        While objEnum.MoveNext()
            Dim ctlItem As New ContentItem()
            ctlItem.DataItem = objEnum.Current
            _items.Add(ctlItem)
        End While
        
        ' Add all the controls
        CreateControlHierarchy(True)
        
        ' Prevent CreateChildControls from executing            
        ChildControlsCreated = True
    End Sub 'OnDataBinding
    
    
    
    '*********************************************************************
    '
    ' CreateChildControls Method
    '
    ' When databind is not called, create the control hiearchy from
    ' view state.
    '
    '*********************************************************************
    Protected Overrides Sub CreateChildControls()
        CreateControlHierarchy(False)
    End Sub 'CreateChildControls
    
    
    
    
    '*********************************************************************
    '
    ' GetRandomContentItem Method
    '
    ' Randomly retrieve one content item and remove it so that 
    ' the same item is not displayed twice.
    '
    '*********************************************************************
    Private Function GetRandomContentItem() As ContentItem
        Dim objRan As New Random()
        Dim contentIndex As Integer = objRan.Next(_items.Count)
        Dim ctlItem As ContentItem = CType(_items(contentIndex), ContentItem)
        _items.RemoveAt(contentIndex)
        Return ctlItem
    End Function 'GetRandomContentItem
    
    
    
    '*********************************************************************
    '
    ' CreateControlHierarchy Method
    '
    ' Add all the content items to the ItemTemplate.
    '
    '*********************************************************************
    Private Sub CreateControlHierarchy(useDataSource As Boolean)
        Dim ctlItem As ContentItem = Nothing
        Dim _displayCount As Integer = 0
        
        ' Check for ItemTemplate
        If ItemTemplate Is Nothing Then
            Throw New Exception("You must supply an ItemTemplate!")
        End If 
        
        ' Update Item Count
        If useDataSource Then
            ItemCount = _items.Count
        End If 
        ' Calculate display count
        If RepeatItems = 0 Then
            _displayCount = ItemCount
        Else
            _displayCount = RepeatItems
        End If
        If _displayCount > ItemCount Then
            _displayCount = ItemCount
        End If 
        
        ' Create each item
        Dim i As Integer
        For i = 0 To _displayCount - 1
            If useDataSource Then
                ctlItem = GetRandomContentItem()
            Else
                ctlItem = New ContentItem()
            End If 
            ' Assign template specific properties
            ctlItem.ItemIndex = i
            
            ' Add the item to the ItemTemplate    
            ctlItem.ItemType = ListItemType.Item
            ItemTemplate.InstantiateIn(ctlItem)
            ' Add the item to the controls collection
            Controls.Add(ctlItem)
        Next i
    End Sub 'CreateControlHierarchy
     
    
    
    
    '*********************************************************************
    '
    ' RenderContents Method
    '
    ' When FlowLayout is table, render an HTML table.
    '
    '*********************************************************************
    Protected Overrides Sub RenderContents(writer As HtmlTextWriter)
        
        ' if flow layout mode, use default rendering
        If _repeatLayout = RepeatLayout.Flow Then
            MyBase.RenderContents(writer)
            Return
        End If
        
        ' Otherwise, render a table
        _alternatingItemStyle.MergeWith(_itemStyle)
        
        _tableStyle.AddAttributesToRender(writer)
        writer.RenderBeginTag(HtmlTextWriterTag.Table)
        Dim i As Integer
        For i = 0 To Controls.Count - 1
            If i Mod 2 = 0 Then
                _itemStyle.AddAttributesToRender(writer)
            Else
                _alternatingItemStyle.AddAttributesToRender(writer)
            End If
            writer.RenderBeginTag(HtmlTextWriterTag.Tr)
            writer.RenderBeginTag(HtmlTextWriterTag.Td)
            Controls(i).RenderControl(writer)
            writer.RenderEndTag()
            writer.RenderEndTag()
        Next i
        writer.RenderEndTag()
    End Sub 'RenderContents
End Class 'SuperContentRotator 





'*********************************************************************
'
' ContentItem Class
'
' Represents a particular content item.
'
'*********************************************************************

Public Class ContentItem
    Inherits Control
    Implements INamingContainer
    Private _dataItem As Object
    Private _itemIndex As Integer
    Private _itemType As ListItemType
    
    
    Public Property DataItem() As Object
        Get
            Return _dataItem
        End Get
        Set
            _dataItem = value
        End Set
    End Property 
    
    Public Property ItemIndex() As Integer
        Get
            Return _itemIndex
        End Get
        Set
            _itemIndex = value
        End Set
    End Property 
    
    Public Property ItemType() As ListItemType
        Get
            Return _itemType
        End Get
        Set
            _itemType = value
        End Set
    End Property 
End Class 'ContentItem 

End Namespace